Derek had gone all out planning Emily's birthday party. He wasn't normally the sort to plan extravagant parties (at least, not the kind that didn't involve alcohol), but he had big plans... (Not that this event could particularly be called extravagant, considering the fact that it was just some of their friends and a cake for the most part, but it was still more than he usually did, so he was going to stick with the descriptor whether it was apt or not.)

"So, Dad..." Matthew said, mischief in his tone. "How's it going?"

Derek shot him a raised brow. "If you're fishing for information, don't bother."

He grinned. "So, you admit there's something going on?" he said slyly.

He just glared at him. "Mind your own business," he snapped.

Matthew just laughed. "Oh, believe me, I am..."

"What's that supposed to mean?"

He just shook his head, mimed zipping his lips.

Rolling his eyes, Derek asked, "So, where's Celeste?"

"Mom wanted to have her overnight, so she should be here soon," he said. "Why? What do you want with her?"

"Nothing!" he said, too quick, too urgent.

Matthew obviously wasn't buying it, though. "You're up to something."

He held up his hands in self-defence. Fortunately, he was saved by Emily's car pulling into the parking lot. "Here's the birthday girl – everyone get ready!"

Silence fell over the gathered crowd.

Emily's footsteps could be heard approaching, along with Celeste's baby babble. "Are we going to see Papa Derek?" Emily asked the child, voice muffled through the closed door.

"Papa?" Celeste asked. Then, louder, "PAPA!?"

The door swung open then, Emily calling out in a sing-song voice, "Oh, Grandpa..." (She loved to tease him endlessly about his being a grandfather.)

As she crossed the threshold into the living room, she was greeted by a clamouring shout of, "SURPRISE!"

Once the initial shock faded, her face split into a rather self-deprecating smile. "You guys know I hate my birthday, right?" she said with a little laugh. She approached Derek, wrapping one arm around his waist and leaning in to kiss his cheek, knowing full well he was the guilty party.

"I tried to tell that to Derek, but you know as well as I do that the man just doesn't listen..." Penelope informed her, the two women sharing a laugh over Derek's pigheadedness.

Nodding, Emily agreed, "I'll forgive him once. But only once..." She winked up at him to show that she was only teasing. Mostly.

Knowing better than to protest, he just nodded along as if taking her words to heart. Even if they both knew that, come next year, he'd do it all over again.

While Emily was mingling with the other guests, Derek had silently slipped away from the party, taking Celeste with him. "Hey, Jellybean," he cooed to the child, "Remember what Papa told you?"

"Secret?" Celeste asked.

"That's right, our little secret." He knelt down in front of her so that he was at her eye level. "We're going to surprise Gigi..." He pulled the little velvet box from his pocket and opened it up to show her the opal ring he'd picked out and placing it in Celeste's little palm. "You have to go give this to Gigi, okay?"

She nodded solemnly, face a mask of baby-cheeked concentration as she squeezed her little fingers around the ring.

Derek smiled at her, kissed her forehead, then turned her around and patted her diaper-cushioned bum in a gesture for her to go find Emily.

Celeste waddled back into the living room in search of Emily. "GIGI!" she hollered, attracting everyone's attention. Then, she paused, stared down at her fist in thought...and immediately stuffed the ring into her mouth.

"No!" everyone shouted at once. There was a mad scramble to reach her and fish out whatever it was she was about to swallow.

Derek reached her first, eyes wide in panic as he fished around in her mouth. "That's not what we agreed on..." he said, though he could never actually be angry with her. Then, since he was already on his knees, he turned to Emily who was watching the spectacle with wide, confused eyes. "Em, I was stupid enough to let you go once – I didn't appreciate what I had at the time. But I'm older and wiser now and I'm lucky enough to have you back in my life. I know better than to make the same mistake twice..." He paused, heaved a nervous sigh. "Emily Prentiss, will you marry me?"

For a few moments, her mouth hung open in surprise, not quite able to believe this was really happening. At length, she gave a watery smile, nodded. "Yes," she whispered. She let out a sound that was half laugh, half sob. "Yes!"

He wiped the drooly ring on his shirt, then slipped it on her finger. Standing, he swept her up in an embrace before pulling back to kiss her like his life depended on it.

"Congratulations!" Penelope squealed. "Guess we're celebrating two things today!"

Matthew and Chloe shared a small smile then. Matthew cleared his throat. "Actually...three things..." he said with a grin.

Everyone turned to him with curious expressions, waiting to hear what it else it was that they were there to celebrate.

Emily looked at her son with a raised brow, silently sizing him up. "No!" she exclaimed, apparently having figured it out without ever needing a hint. "Really?"

He smiled, nodded.

The next moment, she'd engulfed her son in an embrace.

"Well?" Derek said, seemingly feeling left out. "Tell the rest of us non-psychics what it is..."

Chloe pulled a sonogram picture out of her pocket, showing it to the room.

"You're pregnant?" Kristy asked, hardly daring to believe it.

Chloe nodded. "Almost three months along."

Derek approached his son, waiting for Emily to release him, then clapping him on the shoulder. "Listen, kid..." he said quietly, "I love you, but I'm not ready to be a gran- A grand-" He still couldn't quite seem to say the full word. "I'm not old."

Matthew just laughed, wrapped him in a hug. "Face it, Dad. You're a Papa now."