A/N: Thanks to Gerardfan for your review! This version of the story is really just an expansion. The original was my effort at finding a way to bring Emily back before the show did it. So there are obviously things that we know now, characters etc. who are a part of this version, who weren't involved in the original. Hopefully this is an improvement on the original, but not necessarily a replacement.

Also, I've started the edit on the prequel story, just bulking up the earlier chapters, adding some Zac/Emily flashbacks to his childhood and more interactions with the team. When I first started writing that, it was just going to be short chapters, but as the story came to me, it became bigger than I had initially planned, so I'm going back to add to the smaller chapters.

Chapter 5: In the DNA (Ocean, by John Butler)

Zac turned the volume up on the media player as he ran his hands over the books on the shelves. He'd spent so much time reading about protozoa in recent weeks that he felt like his brain needed a break.

Actually, Zac huffed as he took out a copy of Leonard Nimoy's first autobiography, I am not Spock, it had been his supervisor who had suggested he find something to read that was unrelated to his work, as a way to give the part of his brain that focused on math and science a break. It was one of his suggestions when Zac had told him he'd been dreaming of water-borne bacteria.

And I can change the world

I would be the sunlight in your universe

You would think my love was really something good

Baby, if I could change the world

Baby, if I could change the world

The music continued in the background and Zac sighed, putting the book back on the shelf. Spock was a little too close to math and science and he was supposed to be taking a break. "Find something a little bit more abstract than what you've been consuming lately,", had been the advice of his supervisor.

Zac's eyes settled on a favourite of his mother's, a book that she'd read to him repeatedly throughout his childhood. In no way was it a children's story, but Emily Prentiss never really had boundaries when it came to Zac and books. She pretty much let him read whatever he wanted to, from comic books to classics, trashy novels to textbooks.

Zac took the copy of Frankenstein out of the shelf and sighed, running his finger over the well-worn spine. He nodded, moving over to the liquor cabinet with his book and pouring himself a glass of scotch. With beverage and book in hand, Zac made his way over to the couch, dropping down on the soft cushion and bringing his feet up to hang off the edge.

As he sipped the drink and listened to the music, Zac felt himself finally starting to relax. The familiarity of it all made him miss his mom, but not in the upsetting way that it had for the last couple of months. It made him think that he might actually be coming out of this horrible period.

In no way did Zac feel like he was done with his grief, but he was hopeful. He knew that there were plenty of theories about the logical sequence that grief was supposed to take, but in his experience thus far, there was nothing sequential about it at all. He moved back and forth between denial, anger, bargaining, depression, and acceptance, never settling on one. And right now, Zac was enjoying a period of acceptance, content in the knowledge that acceptance that she was gone was in no way accepting that he could forget her. He would never forget his mom, or the sacrifice she'd made to keep him and their family safe.

Zac was starting to feel settled in his mom's home, although he hadn't yet felt compelled to pack up her bedroom or study and claim those areas for himself. For now, they would remain her spaces in this home... a way for him to keep her with him for a little longer. But he had been taking some steps forward. He had recently bought himself some bedding for his own room that matched his style, swapping it out for the bedding his mom had used for guests. He'd also thought about inviting friends around to the apartment for a poker night. All steps that suggested he was currently feeling ok with the status quo… not that he'd have any choice if he wasn't. His mom was gone, and there was no bringing her back. But he was starting to feel some of the fog lifting.

As Zac turned the pages, he heard a knock at the door. He wasn't expecting any visitors, but at least this one had knocked and hadn't just busted into the apartment. He stood from the couch, laying the book face-down on the coffee table, before he headed down the hall to greet his unexpected visitors.

A smile came to his face when he checked the peephole, and he stepped back to open the door.

"Hi Aaron," Zac said as he opened the door with a smile, looking at his new friend and then down at his little companion, a young boy who looked to be about six. Zac knew from the photos that this was Hotch's son, Jack, and Zac was glad that Hotch felt comfortable enough to bring him around. After spending time together in recent weeks, Zac had been getting to know his mom's friend better and felt like they could be friends too.

"Hey Zac," Hotch replied, gesturing down to Jack, "This is my son, Jack. Jack, this is my friend, Zac..." he paused and looked down at his son, "Emily was Zac's mommy."

Jack shied away from the attention, hiding behind his dad's leg, and Zac wondered if he could get any cuter. Zac squatted down and held out a hand, "Hi Jack," he said softly, smiling as Jack took his hand and shook it. Zac tipped his head towards the apartment, "If you want to go and have a look, I think there might be some special toys that my mom kept here just for you."

Jack's eyes grew wide and he looked up at Hotch for permission, Hotch simply nodding in reply. He stepped gingerly into the apartment and then broke into a run down the hall, disappearing behind the wall where Emily had set up a little library nook in the living room, with Jack's crate of toys in the corner.

Zac stood back up and watched Jack disappear, before he turned back to Hotch and gestured for him to come inside.

Hotch took a deep breath as he stepped across the threshold, feeling uncharacteristically nervous at the thought of walking in Emily's apartment, and her not being there. It was surreal. He had been in this home so many times before, and even though Zac was now living there, it felt exactly the same. He half-expected Emily to come walking out of one of the rooms any second, a smile for Hotch and a cuddle for Jack.

"Can I get you guys a drink?" Zac asked, leading Hotch down the hall. He assumed his visitor had mixed feelings about coming back into this place, so Zac was trying to be respectful by giving Hotch some space. Zac knew he had needed to give himself some time to adjust to being in his mom's home, without his mom, and Zac had already concluded that Hotch's feelings for Emily were that of more than just friends.

"Uh yeah," Hotch replied, "That would be great, thanks."

"I just poured myself a scotch, but I've got beer, or juice, water… coffee if you'd like," Zac said nervously, watching Hotch peruse the changes he had made to the living room.

"Oh, just water's fine, thanks," Hotch replied, as he looked around the room, spying Jack in the corner with his toys, "We're just stopping by."

Zac nodded, heading into the kitchen to get the drinks, leaving Hotch and Jack alone in the living room. He figured they could probably use a little time to re-acquaint themselves with the room, and he was glad that JJ had thought to bring Jack's toybox around. Even from the kitchen, Zac could hear Jack squealing with joy at being reunited with the collection of matchbox cars.

Hotch turned to look around the room, feeling Emily in every fibre. He had been with her the day she'd chosen most of the furniture and he had helped her move all of it into the place. He chuckled as he ran his eyes over the ridiculous number of throw pillows that Emily had insisted on buying. She'd told him that sometimes she just needed a small pillow to rest her head on, like when she would lay her head in Hotch's lap so that he could play with her hair, calming her down after a tough case. And sometimes she needed the larger ones, to sit on the floor with Jack while they pieced puzzles together on the coffee table. Each and every throw pillow had a purpose, most of which had involved him and Jack in some way, and that thought warmed him.

Looking up to the mantel above the fireplace, Hotch furrowed his brow, realising that not everything was the same. He made his way over to look at the collection of memories, photos of Zac and Emily, and her parents, throughout the years. He spotted a photo of Zac and Emily, centred in a simple black frame. Zac looked to be only a couple of years old, and Emily was still young herself. There was a young man in the photo with them and, having seen the photo that Emily had kept from her years in Italy, Hotch knew it was Matthew. He smiled softly, knowing what Matthew meant to Emily and glad that Zac had found a way to remember them both.

He looked at the image of a young Emily, holding a baby Zac. Based on the surroundings, this would have been from the day Zac was born. Emily in the hospital gown, sitting back in the bed with a tiny Zac laid against her chest. Hotch's heart warmed at the sight, falling in love with Emily a little bit more at the thought of the strength it had taken her to bring Zac into this world. The strength it had taken her to raise him, to protect him fiercely. Looking at Zac now, as a grown man, he knew Emily must be exceptionally proud of who he had become, and it all started in that moment.

Hotch was roused from his thoughts when he heard Zac walking back towards him, and when a glass of water appeared in front of him, Hotch looked over at his young host and smiled.

"Mom had hidden all of our photos," Zac explained, "She must have told JJ about it, because she showed up last week with boxes of photo albums and Jack's toys."

Hotch nodded, turning back to the photos, "It's nice to see you're finding ways to remember her," he replied softly, running his eyes over the gallery of images from Zac's childhood, "She'd like that."

Their conversation was interrupted when Jack ran over to them, tugging on Zac's jeans and grinning widely, "Can we make this puzzle?" he asked brightly, holding up a puzzle box, "This was Emily's favourite!"

Zac looked up at Hotch and smiled before he turned back to the little guy, "Sure thing, Jack-in-the-box!" he replied with equal enthusiasm, leading Jack over to the coffee table and helping him tip the pieces from the box and onto the table.

Hotch felt his heart constrict as he watched the boys interact. He felt like he'd been doing alright, up until the moment Zac used the same endearing term that Emily had always used with Jack. It actually hurt his heart to hear those words come out of Zac's mouth, using the same delighted tone that Emily had always used with his son.

"Daddy!" Jack called out, causing Hotch to look up quickly and paste a smile on his face, "We need your help."

Hotch nodded, making his way over to the couch and dropping down behind Jack, reaching over him to help turn the puzzle pieces over so they were facing the right way up.

"Daddy," Jack started, looking back at his father, "Can Zac come to the circus too?"

Hotch huffed and looked over at Zac, "Uh… there's a circus coming to Arlington next weekend," he explained, "I'm getting tickets tonight... if you'd like to join us."

Zac looked from Hotch, down to Jack, offering the little guy a big grin, "I love the circus!" he replied happily, "But I'll only come along on one condition…" he paused, continuing at Jack's nod, "That you let me buy the cotton candy."

Jack giggled and held his hand out, "Deal."

Zac chuckled and shook the little boy's hand, before returning to the puzzle and wondering if he should run his question past his new friend, and wondering how to pose the question given the presence of little ears in the room. Zac cleared his throat, prompting Hotch to look up at him, "I'm actually glad that you stopped by, Aaron. I had a visitor the other day," he started, "Not sure if you know him, but I was hoping you could give me some advice."

Hotch nodded, placing a couple of pieces together, "Sure Zac," he replied, "What's going on?"

Zac sighed, furrowing his brow and looking down at the pieces in front of him, "Uh… this guy named Clyde came by the apartment…" he paused and huffed, "… actually, he had a key and let himself in, and I just happened to be at home."

Hotch frowned, looking up at Zac, "You need to change the locks," he said quickly, pointing in the direction of the door, "And get yourself another deadbolt."

Zac nodded, "Yeah, I was pretty freaked out so after he left, I called JJ. She organised for a locksmith to come over right away and she came over too," he explained.

"So what did he want?" Hotch asked, as if he didn't already know. Clyde had been calling Hotch constantly in the first couple of weeks after Emily's death, but the calls had stopped. In no way did Hotch think it was the last he'd seen of the man, and now he had his confirmation. Clyde was still digging around for information on Ian Doyle, and while Hotch would be fine with anyone taking out the bastard, he wanted that privilege for himself. And Hotch had another concern now, that Emily's best kept secret might have been spilled to a man they couldn't necessarily trust.

Zac shrugged, "He said he thought there might be some clues that you guys missed, and asked if he could look around…" Zac paused at Hotch's incredulous expression, and he bit his lip, "I uh… I told him that I needed to check with Emily's parents. He left a card and told me to let him know when Grams and Pop had an answer."

"Does he know who you are?" Hotch asked, his mind racing with questions about what Clyde thought he was doing.

Zac shook his head, "I don't think Mom told him about me," he explained, "And I just said I was a friend of the family…" he chuckled, "I didn't even have to lie, just said that Emily knew my grandparents."

"Quick thinking," Hotch said proudly, "Your mom would be proud."

Zac nodded and let out a breath, "So… what do you think?" he asked, "Should I let him dig around here?"

Hotch shrugged, "Any evidence that your mom had wouldn't be here," he replied, "So there's nothing for him to find… which means you should say yes…" Hotch paused and pointed up to the collection of photos on the mantel, "But I'd hide those somewhere safe when he comes around."

Zac followed Hotch's gesture and nodded, "Good thinking…" he paused, looking back at Hotch, "And in the general scheme of things… should I trust him?"

Hotch huffed, helping Jack fill in the final pieces of the puzzle, revealing a scene of the streets of Paris, the lights of the Eiffel Tower glistening in the night sky.

"Not on your life."

Jack squealed, his face lighting up as he sped down the large slide. Zac glanced over at the boy and laughed loudly, gripping the potato sack he sat on. When they reached the bottom, Jack dropped the potato sack with the attendant and ran straight to his dad, Zac following soon after.

"Daddy! Did you see me? I was going so fast!" the boy cried, jumping into Hotch's arms.

Hotch chuckled and nodded, "I saw it, buddy! That looked like fun," he looked up and smiled at Zac, "You doing alright there?"

Zac rolled his eyes and held his stomach, "Just thinking that riding a potato sack down a giant slide right after eating a beef burrito was probably a bad idea."

Hotch nodded and chuckled again, "Yeah, for a genius I thought you'd be a little smarter than that," he joked. He glanced at Jack, then back up at Zac, who was becoming increasingly pale by the minute. Nodding over to the large grassed area, Hotch pat Zac's shoulder, "How about we go and sit down for a minute or two?"

Zac smiled and nodded, "That's probably a good idea," he replied, clutching at his stomach.

The three of them made their way over to the big empty patch of grass behind the big tent, finding a nice shady spot to sit back and watch the fair. There were tons of rides, tons of people, and at six, the circus' main event would begin. Jack was looking forward to the jugglers, Zac was looking forward to the clowns. And Hotch was just glad to have a happy memory for all of them. He was really enjoying getting to know Emily's son a little more each time they hung out, and he was especially glad to have another Prentiss around to keep Jack happy.

Zac lay down on the grass while Jack spun around in circles, the fairy floss he'd consumed providing enough energy to last him until bedtime. Hotch usually preferred to keep Jack healthy with a limit on sugar, but today was a special occasion. It wasn't often that they had the chance to have fun like this, so Hotch was going to make the most of it. As he sat back, keeping an eye on both of the boys, Hotch made the most of the warmth of the last remnants of sun before it disappeared for the night.

"You've got a good kid there, Aaron," Zac mumbled, watching the small boy play and wondering where he got all of his energy. The more time he spent on his PhD thesis and work, the more exhausted Zac felt, and he wondered if he could bottle up some of Jack's seemingly endless founts of energy.

Hotch looked on proudly, "I know…" he paused and looked over at Zac, "... And so do your parents."

Zac huffed and shook his head, "Aside from the whole conception thing, I only ever had one parent," he replied, opening his eyes and staring at the blue sky, watching the clouds roll over them.

Hotch wrinkled his brow and swallowed hard, the idea of Emily raising this boy on her own, "What about your father?" he asked.

Zac sat up, brushing his hands down his jeans and retying his shoelace, "I only met John a couple of times. He was still in Rome when Mom and I moved back to the States. He went to college in the UK and Mom and I moved to New Haven. And he's always travelled for work, so I never really knew him. I call him dad on the rare occasion that he calls, but in truth, he's never really been around to earn the name."

Hotch pursed his lips and nodded, "When was the last time you heard from him?"

Zac shrugged and looked in the direction of the photo booth, "He was at Uncle Matt's funeral… uh… a couple of years ago," he explained, "But aside from that he called me a few months back to ask if he could come to my graduation…" Zac paused and looked over at Hotch, "… Did you ever meet him?"

Hotch shook his head, "I never met him. I saw him, when he came to visit your mom in the office once… and during that case when we went to his house… but Emily never introduced him to me," he replied, thinking about that awful case, which had almost cost him his friendship with Emily. They'd come a long way between that horrible week and where they were today, but it was one of those moments that could have changed everything. In many ways, it had pushed them closer together, Hotch's mind taking him back to a night where he'd held Emily while she mourned her best friend. Hotch shook the thought from his mind and turned back to Zac.

"Hey, was that when Mom had that sarin gas poisoning? When the priest killed Uncle Matthew?" Zac remarked, looking to Hotch.

Hotch nodded, a memory coming to mind from that week, "I came to the hospital to check on your mom," he replied, "I think you were there with her... I didn't go into the room at the time, just saw you and Peter in there and figured she didn't need to see me."

Zac nodded, sitting up on the grass, "Yeah, I was pretty worried about her, so I flew back from LA the first chance I got…" he paused and shook his head, "I guess I wasn't worried enough, considering what's happened now."

"None of this is on you, Zac," Hotch urged, "You know that right?"

Zac nodded, picking at a blade of grass and twisting it in his finger, "I know... but..." his voice trailed off and he shook his head.

"Your mom did what she did to protect you," Hotch said insistently, reaching over to squeeze Zac's shoulder, "To protect all of us. And I think she'd be really glad that we've met and that we can both learn a little more about her from each other."

Zac looked over at Hotch with a soft smile, "She did a good job of fooling everyone, didn't she?" he huffed.

Hotch shrugged, "We all have our reasons for keeping secrets, Zac," he replied, "Your mom was no exception."

"It's a pretty big secret to keep though… having a child," Zac remarked, "I mean, sure, I was in college by the time she started at the BAU, so it's not like she had to organise babysitters for when she went out of town, but… I've never felt like Mom was ashamed of me, just maybe she was scared what people might think of her."

Hotch wrinkled his brow, "I don't think Emily could ever be ashamed of having a son like you, Zac."

Zac shook his head, "I know… I guess I just always remember what she said people were like in high school..." he paused and looked over to Hotch, who nodded for him to continue, "Mom was always super honest with me about what it was like for her. The whispering behind her back when she turned up to school pregnant, the looks from teachers when the principal made them aware of my existence… she had it pretty tough at school…" Zac paused again and shrugged, tugging at an imaginary thread on the hem of his jeans, "I guess I always figured she didn't tell you guys about me because she was afraid the same thing would happen… at least at first. And then by the time she got to know you all, maybe she felt like it was too late to share."

Hotch nodded and looked up as Jack ran over to them, "Well if it means anything, I'm glad I have the chance to know you now, Zac," he said with a genuine smile as he stood from the ground. He held out a hand to help Zac up from the ground, patting him on the back and taking Jack's hand.

Zac returned the smile and reached down to take Jack's other hand, and the three of them headed towards the big top, "Me too Aaron."

Hotch smiled as he ran his hand over Jack's back, the exhausted boy unconscious the second his head hit the pillow. It had been a good day, running around with Zac, jumping on as many rides as their bellies full of festival food would allow, and laughing endlessly at the slapstick comedy of the clown performance under the big top. He was glad that Zac and Jack were getting along so well, knowing that his son deserved to have as many fun, kind people in his life as possible. And Zac was just like his mom in that respect.

Hotch leaned over and kissed the small boy's hair, whispering goodnight before he made his way out of the room, switching off the overhead light and closing the door behind him.

He walked down the hall, stopping in the kitchen to pour himself a glass of water, before heading straight for his desk. He opened up his laptop, quickly running over the moral and ethical issues of his plan once more, before deciding that he wasn't doing this out of curiosity or malice, but out of care for his new friend.

He opened up the database and typed the names into the relevant boxes, having limited details for his search and hoping that he had the spelling correct. He watched the spinning circle as the computer did its job, waiting for the results to pop up. When they did, he nervously hit "enter" and waited for the page to load.

John Thomas Cooley, DOB: 01/17/1971, POB: Manchester, Connecticut, Current Location: Washington DC

Hotch wrinkled his brow. The man was in DC and, as far as the general public was aware, his son had just lost his mother. They were living in the same city and this guy hadn't checked in with his child. Hotch felt a wave of frustration and disgust wash over him. How could this man not take the time to even visit his son? Sure, as Zac had said, they might not be close, but there had to be some sort of familial obligation to visit your son when his mother died. And by Zac's own account, John had reached out a few months earlier to ask about coming to his graduation, so he obviously had Zac's number. He didn't need to go through Emily anymore.

Hotch shook his head and slammed the laptop shut.

Picking up his cell as he stood and made his way to the couch, Hotch opened up a new message.

*Hey Zac. Just wondering if you're up for a movie night tomorrow? Going to introduce Jack to the classics: Little Rascals and Milo and Otis. - AH*

Hotch switched on the TV and flicked through the channels as he waited for a reply. Sure enough, a second later, he heard the low beep.

*Absolutely. I'm a sucker for a pug-nose pup riding a turtle. I'll bring the popcorn. - ZP*

Hotch chuckled and smiled, texting back the time and other food requests. He sighed and sat back, not really paying attention to the renovation show he'd landed on, instead thinking over the events of the day. He felt like Zac would need someone to talk to, now and in the event that Emily came back to DC, and if his real father wouldn't be that someone, Hotch was more than happy to accept the role.

Zac looked out over the neighbourhood, taking a long drag of his cigarette and letting the smoke drift out of his mouth. He really hated this habit, but he'd been stressing about making this call and needed a little nicotine courage.

He knew that Clyde was waiting for his call, and even though JJ had tried to alleviate some of Zac's concerns about letting him rifle through his mom's belongings, he hadn't felt truly ok with it until he'd run it past Hotch. And that conversation had been a week ago, so really… he'd put it off for long enough.

Zac took one last inhale of the cigarette before he dropped the butt Into the can on the wall. He really needed to stop doing this every time he was stressed. Given his mom's history, this probably wouldn't be the last time her old life came calling, and he needed to find ways to deal with that other than smoking himself into an early grave.

Zac paced back and forth, tapping his cell against his thigh as he walked, before he decided to just do it. He pulled the card out of his jeans pocket and dialled the number into the cell, holding it up to his ear as he waited for the call to pick up.

"Easter."

"Uh… hi Mr Easter," Zac replied, "This is Zac. Emily's…" he cleared his throat, "… friend."

"Oh, hello," Clyde said, "Thanks for getting back to me. I assume, since you're calling, that it's good news?"

Zac huffed, "Sure… you're fine to come around and check her study, if you'd like," he explained, "I'll be home all night."

"Ok, brilliant," Clyde replied, "I can come by around six."

"I'll see you then," Zac said, quickly removing his cell from his ear and ending the call. He had no need to be polite to this guy and, given Hotch's icy reaction to the mention of his name, Zac figured he didn't owe the man anything. Zac wondered why the mention of the man's name prompted Hotch's reaction, if it had something to do with his mom's death. Zac's gut was telling him that there was something going on there, and having a grandfather in the CIA and a mother in the FBI meant it was in Zac's DNA to not trust anyone.

Clyde had asked for access, and Zac would grant it… this time… and even though Zac had granted the access, it didn't mean that he had to trust him. He especially didn't need to share the true extent of his history, or his relationship with his mom.

Folding up the chair and placing it back in its usual spot, Zac made his way back downstairs and climbed in the bedroom. He had an hour to erase any evidence of his relationship to Emily Prentiss.