A/N - This is really one half of a punishingly long 6.5k chapter, so there are further explanations and reveals to come. Thanks again for reading, and for all your support. xx

As circumstances had it, the task of interviewing Beryl Holland eventually fell to Lestrade and Donovan. Forced to triage his priorities, Sherlock had decided that he needed to interview Adrian Frost in person more urgently. Since there needed to be a sworn officer in attendance at an official police interview, that role fell to Jake Dyer. It would be the first time he'd ever led an interview. Sherlock and John arrived at Penzance Police Station to find Adrian waiting in the interview room, and Dyer so on edge he was all but doing jumping jacks by the front desk.

"No lawyer," was the first thing out of his mouth. "He doesn't have to have one, and I guess he figures he doesn't need one, but… I kind of wish he did, you know?"

"You'll be fine," John offered, watching Sally Donovan knock on the other interview room door, open it and go in. "Don't worry about Sherlock or me, just worry about Adrian."

"Don't worry about Adrian, either." Sherlock was facetiously adjusting one of his sleeves. He pulled his right cuff in sudden pique, so hard that he broke the button. With a hiss of irritation, he let the button clatter its way unheeded toward the community noticeboard and shrugged his shoulders twice, as if preparing for action. "I'll do the talking."

"Are you sure that's a good idea?" John asked him, frowning.

"All my ideas are good ones."

John scrubbed one hand over his jaw. "Yeah. Well."

"He's still a suspect, John."

"I know," he said. "Just, look, if I tell you to shut up in there-"

But Sherlock was no longer listening. Across the waiting room, an elderly couple were huddled in grey plastic chairs lined up against the wall. The man was long-legged and barrel-chested, though he must have been closer to seventy than sixty; a full grey beard and large square glasses obscured much of his ruddy, pleasant face. The woman beside him had generous proportions of everything, from her mass of grey curls and aquiline nose to her flat feet. She was digging into her handbag. Eventually she pulled out a sweet wrapped in printed wax paper and handed it to the man, then glanced up at Sherlock, who blinked and nearly took a step back. Grey eyes. Sadie's eyes.

"That's Jackie Monash," he said hollowly.

"Um. Yeah." Jake bounced restlessly off his heels. If they didn't commence the interview soon, he'd launch into orbit.

Sherlock ignored him, crossing the floor—straight past Chris Holland, as if he'd never seen him before—and approaching the woman. She stared into space for a good three or four seconds before registering that someone was beside her, but there was no alarm in her expression as she looked up at him.

"Hello." She ran the back of her hand over her dry nose. Dry eyes, too, though they were red-rimmed, and not entirely from jetlag. Her voice was deeper than her appearance would suggest. Deeper than her daughter's. Sherlock thought briefly of the recording Adrian had sent the police of Maisie's birthday. Sadie, with her bedraggled hair and girlish laugh.

"Mrs. Monash?"

"Yes. I'm Jackie. This is my husband, Jimmy—" Jimmy leaned across his wife to shake Sherlock's hand in a motion of perfunctory masculinity. "Sorry, I don't think I know you."

"Sherlock Holmes."

At this she paused in the very act of shaking Sherlock's hand. Her palm rested in his. "You're… you're the great detective."

Sherlock briefly dipped his head; a gesture somewhere between a nod and a bow. "I'm Sherlock Holmes," he said. "And I'm going to find Sadie and Maisie. After that, Mrs. Monash, you can make up your own mind as to whether I'm a great detective."

She squeezed his hand between his. "God bless you."

~~o0o~~

"Sorry we're a bit late," Dyer apologised breezily, admitting Sherlock and John into the room and shutting the door behind them with one shoulder. He garbled out a hasty preliminary to the interview for the benefit of the tape recording, then passed a cup of coffee across the desk to Adrian. Adrian ignored it, even though he looked like he hadn't slept since Siobhan's attempted suicide.

"Why am I here?" he demanded in a croaky voice. "I told you. I don't know what happened to Brett, and I don't know where Sadie and Maisie are. Siobhan needs me-"

"All right, let's talk about Siobhan, then; the sooner we talk, the sooner you can get back to her." Sherlock's gathered his coat up around his legs and sat down. "How do you feel about children, Adrian?"

He blinked. "Sorry, what?"

"Children," Sherlock continued, straight-faced. "I noticed you don't have any of your own."

Dyer cleared his throat and leaned back in his chair a little, rapping a pen against the desk until a glance from Sherlock stopped him.

"Well," Adrian said, shrugging. "No; well spotted. There's time. Siobhan's only thirty. Not ready yet."

"No, you're ready," Sherlock said. "Siobhan isn't."

"I don't understand," Adrian said.

"You already know that Siobhan attempted to hang herself in your bedroom on Monday." Sherlock glanced down at Adrian's hands. Steady, though he was picking at his fingernails. "What you mightn't know is that if it weren't for CPR, Siobhan's last words might have been, If you only knew what he was like, you'd say it was a pity he didn't lose both his eyes."

"I don't-"

"We were talking about your brother Ethan, Adrian. One of the things that struck me—struck all of us—when he we went to interview Siobhan and her parents was that your wife seemed like a kind, hospitable woman. She offered us a cup of tea, for example, and was upset that her mother hadn't. And for her to think it a pity that Ethan wasn't permanently blinded? Just because he's a drug addict?"

Adrian pressed his tired eyes with the heels of his hands. "I wasn't lying when I said Ethan was a junkie," he finally said.

"I know." Back in London, Gregson and Parnell had tracked down Ethan Frost and visited him at the grubby block of council flats he now called home. Grubby little man, too, by all accounts. Meth. He'd had weeping sores on his face, and his hair had probably last been washed when Blair was in Downing Street.

"I wasn't lying about him getting into deep shit with his dealer, either."

"I know. Where you started lying was when you told us Ethan came to you for help. In actual fact, he came to your home not for help, but to rob you."

"He tried to, anyway." Adrian scrubbed at his hair and bowed his head for a second, then let a breath out through his mouth. "How he got it into his head that we had anything worth stealing, I'll never know, but that's the drugs for you—those skeezy bastards would sell their own children for a fix."

Silence fell, so profound that they could hear Lestrade and Donovan interviewing Beryl in the adjoining room.

"What did Ethan do for a fix?" John asked him quietly.

"I wasn't home. Siobhan gave him our key cards and PINs and everything, but… I guess he thought we had something else. Money hidden in the house, or something."

"And when he wouldn't believe Siobhan that you didn't," Sherlock said, "he raped her."

Adrian flinched, as if Sherlock had struck him. After another two breaths through his mouth, he nodded. "He had a knife," he said. "I mean, it wasn't… it wasn't about..."

"Of course not," Sherlock said. "Rape is not about love, and it's only tangentially related to sexual desire. When Ethan could not take your money—money he felt entitled to—he retaliated by taking your wife's body. In his mind, another theft. Why didn't you go to the police?"

Adrian snorted. "Mr. Holmes, Ethan's been in trouble since he was twelve. You know what the police have done about it? Nothing. They keep giving him community sentences, sending him to rehab, making him rake leaves to show he's sorry. They've put him away twice—six month sentences. Both times, all he did was learn how to be a better criminal when he got out again. You think six months is a good enough sentence for what he did?"

"He'd get a damn sight more than six months for that," Dyer said. His face was as pleasant as usual and his voice calm, but his hands were bunched into tight fists. "The maximum penalty for rape is life."

"Since bloody when has anyone ever got life for rape? That's what Siobhan got."

"And what Ethan got, too, after you set him on fire," Sherlock said. "Your ingenuity and patience is to be applauded. To pretend to be doing your duty as a good older brother, helping poor Ethan out with an insurance job. Putting out the fire just in time, calling the ambulance. You could have saved yourself the effort and just killed him."

"Like I said," Adrian said. "Life sentence."

For half a minute, the only sound in the room was the hum of the fluorescent lights. From behind the partition wall, they could still hear faint voices. By the sounds of things, Lestrade and Donovan were both giving Beryl Holland a bollocking. That didn't happen often. Despite their differences, Lestrade and Donovan made a great partnership. But their interview method was usually good-cop-bad-cop. When they were both bad-cop, the suspect was liable to come out of the interview room crying.

"What you didn't know," Sherlock said carefully, "is that Ethan did more than rape Siobhan. He also made her pregnant. With Maisie."

Adrian sucked in a breath. The sort of sound a man might make if he'd been stabbed in the back.

"She never told you—probably because she intended to terminate the pregnancy and didn't want to hurt you, or for you to try to change her decision. You were serving your sentence in prison, and no doubt Siobhan thought the subterfuge easier on both of you."

Adrian's mouth was open, his bottom teeth trembling in a row; but it was a few attempts before any coherent words came out of it. "Are you insane?" he finally got out. "I would never have asked Siobhan to-"

"But someone did, Adrian. Someone did ask her to carry that baby to term, and let them adopt it. Her brother, Brett."

Silence.

"Brett and Siobhan had been at the mercy of their controlling, mean-spirited mother since childhood, and obviously formed a close bond," Sherlock went on. "Close enough that while Siobhan couldn't tell her own husband she was pregnant, she could and did tell her brother. She thought he would be supportive of her choices, as he'd been all their lives. But this was different for Brett. Sadie had been trying to conceive a child for twelve years. How could he bear it that his sister conceived from a single encounter, and how could he cope seeing her have an abortion? He couldn't. He must have begged. And Siobhan—Adrian, your wife agreed. She agreed to have a child for Brett and Sadie."

"Oh my God." Adrian put his face in his hands.

"She's not quite your God, but you're lucky to have Siobhan, put it that way." Dyer pulled a sheet of paper out of his manila folder. "This is the birth certificate we were originally given for Maisie," he said, passing it over the table to Adrian, who took it with shaking hands. "It's pretty obviously fraudulent, once you get a good look at it. After a bit of digging, we discovered that Maisie Rose was born to Siobhan Ellen Frost at St Ives Hospital on October 9, 2014. Seven pounds, five ounces. There's a blank space on the real certificate where the father's name's meant to go. They were both released on the 12th, and Siobhan immediately initiated adoption proceedings with Brett and Sadie Holland. By the time you were released from prison in February, everything had been sorted. Brett and Sadie were living in Cornwall with their baby daughter, and Siobhan was back in London, willing to try to pick her life back up again, but she couldn't quite forget. Who could?"

"The perfect aunt," Sherlock said. "And she was prepared for this to go on for the rest of her life, until Brett was murdered and Sadie and Maisie went missing. She must have known that it would come out in the investigation that she was Maisie's birth mother; that you'd find out she'd lied to you about it for years. And then we came to the flat and asked her questions about your brother that brought it all back to her just how bad this could get, even if Maisie was recovered alive and well. She was prepared to die rather than face losing you."

"Oh my God," Adrian said again. "You think I'd leave Siobhan over a thing like… holy shit, what is wrong with you people? I'd never ask Siobhan to carry a rapist's baby! And I'd never leave her or hurt her because… wait..."

The penny dropped. he screwed his eyes shut and took a few deep breaths.

"Take it easy, mate," John said.

"You think—you think I found out and hurt Brett." Adrian completely ignored John. "You think I'd hurt Sadie and Maisie? I didn't know any of this, Mr. Holmes, and even if I—"

"You didn't know, but you do now," Sherlock said. "You know what Siobhan went through to get Maisie into the world. So if you even suspect someone of hurting her, we need to know. Now."

"I don't know!"

"Okay," Dyer broke in. "Okay. So why don't we go back to what you do know, Adrian? Or things you might think."

At this, Adrian looked genuinely puzzled. "What do you mean?"

"When us detectives have a murder to solve, we sort our suspects out among ourselves by elimination. Was it Joe Blow? Could be, we put him in the 'maybe' basket and follow it up. Was it Bill Smith? Nah, he has a perfect alibi. And so on. Let's play that game now. Someone killed Brett, and all the evidence points to it being someone he knew. So how about I say a suspect, and you tell me whether you think they could have done it or not, and why? Impartially, the way we work in the police station. So. What if it was Sadie herself who killed Brett? Can you think of a reason she might've wanted him dead?"

Sherlock mentally gave Dyer a tick of approval. Excellent suspect to start off with, not requiring Adrian to betray his wife or his in-laws.

"No," Adrian said, quickly but not suspiciously so. "I'm not going to tell you Brett and me were like brothers or anything, but we got on, and I think I'd have known if Sadie was ready to do him in over something."

"Even though the last time you saw them was Christmas?" Dyer asked innocently.

"Let's not do this trying-to-trap-me bullshit, okay? We were here in Mousehole last week. We were all here."

"By 'all'?"

"Chris, Beryl, Siobhan, me and Derrick. They came down Wednesday morning. But I really did do my back in at work on Wednesday, and I didn't get here until four in the morning on Friday. I didn't see Brett, Sadie or Maisie before they went missing that morning. I really haven't seen them since Christmas."

"We know Beryl and Derrick were here on Thursday," Sherlock said. "They had a row in the corner shop opposite the promenade on Thursday morning. Foolish of Beryl her to make herself so conspicuous, then lie about ever being here. Do you know what they were having a row about?"

"No, because I wasn't there."

"Do you know anything?" Sherlock pressed his palms against the table.

"Sherlock," John muttered.

"Because," Sherlock continued, as if he hadn't heard, "I find it difficult to believe you went along with this idea, to the point of following the group all the way from London by yourself, but didn't even stop to ask what the purpose of the visit was. Clearly it was not intended as a friendly family reunion."

Adrian rubbed his eyes with both palms. "When I got out of prison," he said wearily, "I came home to find Chris and Beryl had moved into our house. Said they'd done it to keep Siobhan company."

"Did you believe that?" John asked.

"No. But I didn't know what else to think. I knew they were hard up for a quid, but I don't go around asking for the details on their bank accounts, right? Siobhan hated it, and no bloody wonder, the way her mother talks to her."

"Yes, we saw," John said, with thinly-veiled disgust. "What about her dad?"

Adrian shrugged. "Ignores her, mostly. Ignores everyone. Never seen a bloke so good at turning off. I s'pose he learned in self-defence, being married to Beryl. Anyway, it's been years since those two invaded and I want my bloody in-laws out of my house. But every time I suggest they go look at a flat of their own or something, Beryl has a pink fit about how they've got no money and if Siobhan and I turn them out, they'll end up living on the street, you know, the whole nine yards of it. The way I see it, Dr. Watson, that isn't my problem. They've both worked all their lives. How is it that they're so broke they need to cadge off us forever?"

"What did Siobhan think of you moving her parents along?" Dyer asked.

Adrian snorted. "Siobhan wants to adopt every stray cat and abandoned baby bird she sees," he said. "She wouldn't have it. All her mum had to do is cry poor and Siobhan gave in. Literally crying poor—Beryl turns the waterworks on whenever she doesn't get her own way. And then she started talking about how Brett and Sadie owe them money and won't pay it back."

"When did that start?" Sherlock asked.

"Dunno, maybe September?" Adrian shrugged. "I know Siobhan said something to Brett about it when she went down to see them for Maisie's birthday. I don't know exactly what Brett said, but it must've been 'no'. There were one or two rows over the phone. And then Beryl and Chris are going down there to confront them in person and demand their money back, and here's me following up behind to—"

Silence.

"To what?" Sherlock prompted him.

"To stop someone from getting killed, is what I was going to say," Adrian mumbled into his collar.

"And who did you think you were going to have to stop from murder?" Dyer asked. "'Beryl has one hell of a motive. Unfortunately, mate, you all do. I suggest you tell us everything you know about what the five of you got up to last week."