The Watsons lived four houses away from the corner in a row of connected terraces. Sherlock and Lestrade were obliged to go all the way to the corner to avoid being seen by anyone looking out of the Watson's windows. Sherlock knew that John and Molly lived next to an elderly couple named Armfield on one side, on the other a fortyish man named Patwary, who, in weeks immediately before and after Charlie's birth, had held loud parties every Friday and Saturday night. But as for the residents of Number One, he was completely ignorant. There was no time to explore their house and make any deductions about them.

The houses backed onto a long, narrow strip of grass, barely wider than a footpath, that someone from the council with a sense of humour had labelled a 'nature reserve'. Since Kitty Reilly and her colleagues were still visible on the opposite cross-street, Sherlock and Lestrade hurried around the corner on foot and then up the street behind, until they sidled back around the side of Number One. They were now in full view of the police unit outside, but nobody looking out the window at the Watson's could have seen them approach that way, and neither could the press.

"Give you a hint," Lestrade said. "Go through the attic."

Sherlock blinked. "Sorry?"

"The houses along this row share attic space. If you can get into this flat or the one behind, get into their attic and then just go along until you reach John and Molly's. No walls or anything between them. Comes out at the end of their hallway, though, so be careful they don't see you coming down."

"How do you know?"

"'Cause I've been up there, that's why. I helped Molly move all the spare-room furniture into the attic when she cleaned it out for the nursery."

But Sherlock was no longer listening. Instead, he was looking up at the house they were standing in front of. The bottom level of this side of the house only had one window - that of the utility room toilet. It was far too small for an adult to get through, and it would be a dangerous waste of time trying. He looked up, shielding his eyes with one hand against the glare of the sunset. There was a second-storey window that he might be able to get into. In the Watson's virtually-identical house, it was Charlie's nursery window and locked up like Fort Knox. But having been evacuated in a hurry, the residents here had left this window slightly open to let in the summer afternoon breeze. "Help me up," he said.

Lestrade reluctantly got down on his knees in the damp earth under the window to give Sherlock a leg-up. "You sure you don't want me to come in with you?" he said, grunting a little as Sherlock used his interlaced hands as a step.

"No." Sherlock made it up onto the utility room windowsill and started searching with his fingers for the lower ledge of the window above it. "You'd slow me down. I'm faster and quieter on my own."

Lestrade nodded. "Okay," he said. "Good luck. Try not to do anything st-" He stopped himself. "Actually, do all the stupid things you like. Just get the pair of you out of there alive, that's all I ask. See you soon-"

"Dad!"

Lestrade turned. As Sherlock reached the second-floor window, he looked down to see that Melissa's car had joined those parked at the corner. Matthew scrambled blindly across the street and ducked under the police tape without even slowing down. Lestrade, astonished out of his reserve, grabbed him in something between a bear hug and a rugby tackle, so hard that it nearly knocked both of them down onto the nature-strip grass.

But Lestrade's parenting was no longer Sherlock's concern. He'd already crossed the bedroom and was on the landing, hunting down a chair so that he could access the crawlspace above.

"Where have you been?" Lestrade clutched at Matthew's arm, as if he was three years old and likely to make a dash across the street if he wasn't held onto. "We've been worried to death-"

"They said you were dead, it was on the news!"

"Yeah, well, they were exaggerating. And you're grounded. I don't care how old you are, you're grounded until you're thirty…" Glancing over Matthew's shoulder, he could see Melissa get out of the car. But instead of crossing the road she stood against the driver's side door, only unfolding her arms for long enough to give him a dry little wave.

"I didn't know, Dad," Matthew was saying. "I didn't know it was Ed and Cait -"

"I know you didn't. Where have you - do you realise - oh, call your mother..." Lestrade pulled his phone out of his pocket and shoved it into Matthew's hands. "Call your mother, quick; tell her you're okay- you are okay, right?"

Matthew nodded. Then he glanced reluctantly at the mobile phone he held, and swallowed. "Can't you call her for me?"

Lestrade shook his head. "Not a single chance in hell. You're the one who ran away, not me."

"She's going to kill me…"

"Yeah, probably she is, but she's been worried sick, Matty. Take your licks. You deserve them."

As Matthew called Julie, Merivale made her way back over. "Calm down," she said to Lestrade. "I'm not coming down on him, he's obviously not a suspect anymore. But he could maybe help us out in getting to know these kids a bit better. How did Sherlock go?"

"Got into the flat on the corner okay," Lestrade said. "As for how he'll go getting John out…" He shrugged.

Sherlock was in a cold sweat.

John and Molly's house was small, as they went, and although he'd sat listening for the best part of a minute, he didn't know for sure where the Trent kids were. Even if they were both downstairs and he could crawl out from the attic unseen, he had no guarantee they'd stay downstairs. Finally, he managed to clear a space large enough for him to climb down through it. He listened for another few seconds, then let himself down feet-first. He hit the carpet as lightly as possible and immediately ducked into the bedroom, taking temporary shelter behind the door so he could plan what to do next.

He could smell vomit.

After a quick listen revealed that both Caitlin and Edward were downstairs and their hostage was likely to be also, Sherlock ventured out from behind the door. Instantly, he saw the source of the smell, lashed all over the stair carpet. Before he could make too much of this, though, he heard something that chilled his blood: a choked groan from downstairs.

He moved around the landing to a spot where he had a direct view down into the front passage, the kitchen and part of the living room beyond it. By getting down flat, chest and chin brushing the carpet, he could just see that John was crouched on the living-room floor on his knees and elbows, palms resting on the back of his head. But in another second, the groan was repeated, and Sherlock realised it wasn't coming from John. He crawled further along the landing until he could see Edward, sprawled out on the floral-print sofa. There was blood from one end of it to the other. More was coming from his mouth and nose, and his heavy, gurgling breaths could be heard all over the house. Caitlin stood over him, shaking him.

"Ed…?" she ventured in a small voice. "Ed… are you awake…? Get up…"

Edward slapped her away, or tried to. His blunt reflexes missed her arm by several seconds.

Caitlin turned to John. "Do something!" she screamed at him.

"He's concussed," John mumbled. "Needs a hospital…"

Sherlock was barely listening. Edward Trent's health was the least of his concerns, and he had just run a quick scan of the room, homing in immediately on the two bottles on the dining table, one upright, the other on its side. Both empty. Of the three people in the room, only Caitlin seemed relatively unscathed. And yet, John had said that Edward had a concussion, not a case of poisoning…

"He can't go to a hospital," Caitlin snapped. "You help him! You're a doctor…"

John chuckled; a grim, low sound that was muffled by the carpet he was still crouching on. "Should've maybe thought of that 'fore you poisoned me," he slurred.

Then he stopped.

He was looking out the glass doors that led to the courtyard and the small grassed area outside that Molly persisted in calling a garden. In a few seconds, though, Sherlock realised that John wasn't really looking outside. In the dimming afternoon, he could see a reflection of the staircase behind him. And he could also see Sherlock himself, not-so-stealthily concealed on the landing.

For God's sake, John, stop it!

As if he'd heard, John turned his gaze back to Caitlin. But before he did, Sherlock thought he shook his head slightly.

Then he heaved vomit the colour of dishwater onto the carpet.

This seemed to pose Caitlin. She stood staring at her brother as if he were some sort of exhibit in a zoo; then she stepped over to where John crouched, still dry-heaving. She lifted the gun and levelled it at his forehead, just as he looked up at her.

"Oh," he said, still breathless from the last round of heaving. "For God's sake. Finally."

Quick as a whip, John grabbed at the barrel of the gun with his left hand, using the leverage to pull himself to his feet and turn Caitlin away from him. With his right hand, he grabbed at her free arm and locked it behind her back. She screamed in pain and dropped hard onto her knees, just as Sherlock reached the bottom of the stairs.

Crick.

John flicked the safety catch off the Browning and shoved it flush against Caitlin's left temple.

"Doesn't work with the safety on, Caitlin," he said. His jacket had slipped down off one shoulder, and he shrugged it up again. "Sherlock, don't worry about Edward, he won't be getting up in a while. Grab the phone, will you? Tell Merivale she can let her lot in now, we've got one of them unconscious and the other one on the floor doing exactly what I tell her."

But Sherlock barely registered the tail end of John's instructions. He stared at John in stark disbelief. "But… but you…"

"Oh, for God's sake." John rolled his eyes. "I'm not concussed, Sherlock, I was faking it. Harry's hit me harder than that."

Sherlock opened his mouth to reply, shut it, opened it again. "But," he finally protested. "You just took poison!"

John swayed a little on his feet, lost his balance, staggered a step or two. "Yeah," he said. "Mmm. About that…"

John insisted on walking out of his own house under his own steam and did it, though not for long. No sooner had he been reunited with Molly and Charlie than he was made a reluctant inmate of one of the waiting ambulances, though he absolutely refused to let that ambulance actually go anywhere. After Lestrade had helped Merivale with the arrest of Caitlin Trent and seen her unconscious brother rushed off to the hospital, he left Matthew at the car with Melissa and wandered over to where John sat under the glare of greenish fluorescent lights. He was holding Charlie in one arm and having his blood pressure taken on the other. Molly sat beside him, and Sherlock was hovering, arms folded nervously, at his shoulder.

"What is it?" John asked the paramedic, almost before she'd loosened the pressure sleeve.

She gave a long-suffering smile. Less than twenty minutes with her patient had obviously frayed her nerves a little. "80 over 60," she said. "Which means-"

"Which means you need to take a second reading." John sighed and offered her his arm again. "Fine. I'm a lot better, though. It's come up, just in the last half an hour."

"Dizziness?"

"Better."

"Did you actually lose consciousness while you were in there?"

"Not that I remember. Doubt it."

"How's your nausea? Any more vomiting?"

John indicated the half-full cup sitting between him and Molly, just out of Charlie's reach. "I'm drinking this without a problem," he said. "I'm starving, though. And a decent meal will help me metabolise the medication. No offence, but I don't think hospital food is going to help with that."

"If you don't want to go to the hospital," she said, "we can't make you. But you'll be refusing against medical advice."

"For God's sake," Lestrade said. He reached out as if he was going to punch John playfully in the shoulder, then stopped himself at the last second. "Just stop being stubborn and go to the bloody hospital, you."

"Oh, Greg, stop." Molly made a face. "The more you tell him to go, the more determined he is not to. I've had to reverse-psychology him into taking the bins out all year."

John half-smiled at her. "You know me so well, Lolly," he said, reaching out to tweak a lock of her hair off her forehead.

"Lolly?" Lestrade echoed, breaking into a grin.

"Shut up," John said.

"I don't understand," Sherlock broke in, in tones that implied he'd been cheated out of a perfectly reasonable murder by a random miracle. "You took a cyanide pill. How are you… not dead?"

John smiled wryly. "You really want to hear it?"

"What?" Sherlock looked the picture of innocence.

"You want to hear what happened? You're not going to make some smart-arse remark about how you'd have done it better and I'm just an idiot?"

"John."

John nodded. "Okay," he said. "Well, you know, I was just doing whatever was going to keep me alive, Sherlock. They made me sign a confession for their father's murder. Wasn't worth the paper it was written on, so I did it to shut Edward up. And I figured two things out pretty quickly: Donovan hit Edward hard enough that he was bound to collapse sooner or later, and wherever Caitlin was in Witness Protection, it was somewhere she didn't learn to use a gun. She barely knew the trigger from the barrel. She held it… you remember when I first showed you how to use the gun?" He looked over at Molly, who flushed in embarrassment. "Caitlin held it the same way you did - on its side. Yeah, it looks cool, but completely useless if you're intending to shoot. So there was a big chance everything Caitlin knows about guns comes from movies, and there was no way she'd even know how to take the safety off."

"I thought you'd shown your hand when you were hinting around in front of them that you had a gun," Molly said. "But… you did that on purpose? You were trying to get Caitlin to search you, find the gun, and think you didn't want her to have it?"

"Yeah. All I could think was, if Caitlin changed her mind and picked up a knife instead, I might be in real trouble. So anyway, those two got up to all sorts with drowning people and walking them off castle walls and posing them in bathtubs. They thought they were smarter than everyone else - that's why they kept leaving those notes. Why Edward texted me. They weren't just going to just shoot me if they could help it, they wanted it to be clever. Except there was no chance they'd play the pill game fair. If I picked the harmless pill or told them I wasn't going to play, then they might just shoot me."

"So-"

"So first I had to guess what poison they'd use. I remembered Greg saying that the poison in the original case was cyanide, and anyway, only a cyanide would drop you stone-dead in a minute or two."

"Or a tetrodotoxin," Sherlock said.

"Even a tetrodotoxin would probably take longer," Molly objected.

"Anyway," John said, before this could turn into a discussion on Advanced Toxicology. "I was pretty sure it was cyanide, all right? The one in front of her, not me. She looked at it, twice. And Greg, do you remember when we were at the hospital after the rectory burned down, they thought you might have had cyanide poisoning from the smoke inhalation? They gave you something strong to inhale and a couple of injections. Sodium Nitrite and Sodium Thiosulfate."

"Yeah," Lestrade said, though he sounded uncertain. "Yeah, I think I remember that. I felt worse after that than I did before."

"I thought those might come in handy and stocked up. When I figured it was only a matter of time before Caitlin wanted to play the pill game, I went into the bathroom and gave myself the antidote injections." He shut his eyes for a second. "You're right, Greg, you did feel worse after. They'll keep you alive, but they'll completely bottom out your blood pressure. Which, you know, I was pretending to have concussion so that helped it look real, but if I passed out-"

"They were unlikely to force you to take poison while unconscious," Sherlock said. "It might have bought you some time."

"Do you want to hear this or not?"

Sherlock mimed a zipping motion across his lips before John continued.

"I had to get the game moving after that, since the antidote wears off. I knew you were on your way, Sherlock. Edward was getting worse - he had about as much chance of using that crossbow as he had of driving a car in that state. Once I could get Caitlin to believe I was as good as dead, get her to bring the gun close enough, I could disarm her."

"Which you did."

"Which I did." John shifted Charlie on his knee. "And I threw up most of the bloody capsule anyway, but I didn't really plan that."

Molly took a deep breath and looked up at Sherlock, her dark eyes shining. "See," she said. "I told you he was clever!"

"Yes," Sherlock said, sniffing. "Yes, I suppose that was… clever of you, John. Though I can't fairly describe refusing to go to hospital as intelligent."

"I don't need hospital treatment," John groaned. "I need a good night's sleep, in a decent bed." He looked over his shoulder at the house. "And that's a crime scene," he said, "especially if Edward doesn't make it. I don't think the police are going to let us back in there for a while."

Sherlock cleared his throat. "I know somewhere you can stay," he said.