DI Lestrade may have employed the help of Sherlock Holmes over the years, but there was one thing he was confident of on his own: he could spot a liar at a hundred paces.

He didn't always know why someone was lying, or what the truth was, but the simple fact that he was being lied to rarely escaped him. Just something about the twitch of a lip, or an unblinking stare, or too much blinking, or the movement of someone's thumb. Lestrade was not used to self-analysis and would never have been able to work out on his own how he knew someone was lying, but it was probably innate and had been honed from years of experience. The Holmes brothers could work their way around him, but few others ever had. Hayley had told him her first serious rigmarole at the age of twelve; she hadn't even finished telling the lie before she found herself realising what a lost cause it was and confessing to it.

And while CSI and the other crime shows that filled weekday television may have claimed otherwise, Lestrade had been a police officer for thirty years, and this he knew: generally speaking, criminals were idiots.

Most of them didn't even try to avoid being caught. Ted Bundy, for example: considered the classical 'clever' serial killer, the sort of murderer people made movies about. But he prowled for his victims on the crowded banks of a lake – on a public holiday - by driving a bright gold VW Bug right up to them and announcing loudly, "hi, my name is Ted." Then there was Peter Sutcliffe, the Yorkshire Ripper; he went driving around a known police checkpoint with a prostitute in the front seat of his car, false plates on the outside, and a hammer, knife and rope in the back seat. Then there was Dennis Nilsen, who kept his corpses around for company - when the decay got too bad, he flushed bits of them down the loo and was shocked when it buggered up the plumbing for the whole block of flats he lived in.

Idiots.

James Moriarty had been different, but James Moriarty was dead, and criminal masterminds of his calibre were rarely seen outside of prime-time television. Lestrade was confident that if Ralph Inglis lied to him, he'd know, whether Sherlock Holmes was lying in a hospital bed or not.

The young doctor - according to Lestrade's notes, Inglis was thirty-three – arrived at New Scotland Yard promptly on time, or a little before. The downstairs reception called through to Lestrade's phone and he went out to the main open-plan office area. Dyer was sitting at his computer, and he whistled to get the young constable's attention.

Dyer looked up, as eager-to-please as a spaniel. "Sir?"

Lestrade beckoned with three fingers. "Want to help me interview a witness?"

Technically, Ralph Inglis was not a suspect. Or rather, technically everyone involved in the Bartlett case was still a suspect, including Bartlett himself.

"You can ask me the same question a million times, but you'll get the same answer every time," John was telling Sherlock just at that moment. As promised, now that Sherlock had showered and dressed and brushed his teeth, he was regaling him with the findings of the night before.

"I want your answer to be correct, not necessarily consistent," Sherlock said.

"And it's both. Absolutely no residue in his trachea. Very small traces on the inner parts of his lips and on his tongue. Traces on his oesophagus. Stomach contents were nothing but bile, aspirin and chloroform."

"And absolutely nothing else?"

John shook his head. "No, and that's odd," he said. "Unless someone had been recently starving him or something, you'd think there'd be something else there…"

"No signs that he was starved?"

"No, I wouldn't think so. Malnutrition, yes, but he wasn't underweight and there were no signs of systematic starvation over a long period. Mind you, having tapeworm wouldn't have helped... Oh. There was also about a hundred mils of water in his stomach, but he obviously had that with the aspirin."

"Which means he died well before Addie claims to have found him at one that morning."

"Yep… probably at around the same time he took the aspirin, I'd say... nearly four hours before she said she found him. She might've been lying about everything else, but she was probably telling the truth that his toe felt cold."

Sherlock contemplated this in silence for a few moments. "You're absolutely sure?"

"Yes. Both of us were, and both of us will continue to be no matter how many times you ask the question, Sherlock. Suicide. That Bartlett took the chloroform voluntarily is the only thing that fits the medical evidence."

"Dr. Inglis."

"Ralph, please."

Lestrade winced. He hated this buddy-buddy stuff with his suspects, but if Inglis wanted to be addressed by his first name, there wasn't much he could do about that. The man sitting opposite Dyer and himself in the witness chair was a fresh-faced, pleasant looking man, all blue eyes and rosy cheeks and, so it seemed, nothing but middle-class wholesome morals. Dark hair clipped very short. Designer stubble. The sort of pretentious berk that usually put Greg Lestrade's hackles up.

"Ralph," he corrected himself. "I'm glad we could talk, finally. We've intended to have a chat with you for some time, but things came up. Quite a lot came up, actually."

"How is Addie doing?"

Lestrade frowned for a second. Addie? Quite an intimate name for her doctor to address her. But then, hadn't she asked him to call her Addie when he'd interviewed her the other night? Still, might be worth chasing that one up. He scribbled Addie in his notebook.

"Haven't heard this morning," he said in an offhand way, hoping Dyer would be able to hide his own surprised expression, or at least shut up about it. "She's still being remanded in psychiatric care. It sounds like she really needs it."

"God, the poor woman," Inglis mused. "I mean, it must be horrible for her to be on her own at a time like this. I can't even imagine being locked up in…" He trailed off.

"It's for her own good." Lestrade was stone-faced. "By all accounts she's very unstable… attacked several of my colleagues the day before yesterday, two of whom were left bruised and bleeding. And, of course, she's just lost her husband."

No sign on Inglis's face that this had ever really occurred to him before. Obviously, not too many of his friends and family mourned the passing of Edwin Bartlett.

"How long have you known the Bartletts, Dr - er, Ralph?"

"Four years," he said readily, nodding his head as if convincing himself of it. "Though I didn't really know Ed very well."

"You knew him well enough to call him Ed," Lestrade remarked.

"Everyone called him Ed."

Lestrade shrugged. Beside him, Dyer was diligently writing down shorthand at a rate of knots. "So you know Addie Bartlett 'well', then," he said. "Should I take that to assume that you knew her in a non-professional capacity?"

"We were friends," Inglis admitted guardedly.

"But you're not friends anymore?" Dyer pointed out the tense before Lestrade could stop him. "I mean, she's not dead, Dr. Inglis."

Inglis looked at him for a few seconds in silence. "I care about Addie," he said bluntly.

"Yeah, it sounds like you do," Lestrade decided to go with Dyer's tactics for the time being- after all, Inglis seemed to be responding to them. "Are you sleeping with her?"

There was a stony, shocked pause for a second or two. "No," was the offended answer.

And that, Lestrade reflected confusedly, sounded an awful lot like the truth. He shrugged.

"No offence meant. From what we hear, she was sleeping with a few people, and Edwin wasn't one of them," he said. "Did you know anything about that?"

"Why would I?"

"Answer my question, and I might think about answering yours."

Inglis chewed on his lip for a while. "I can't betray the confidence of a patient. It's against the law."

Lestrade nodded. "Okay. But you know full well I'm just going to go and get a court order requiring you to answer my enquiries. I'm also going to get a search warrant and have a team go through every single inch of your place and your car with a fine-toothed comb. Your choice. Easier if you just talk."

Inglis sighed heavily, glancing up at the security camera for a split second. His hands were on the table in front of them, and he clasped them hard. "Yes, I knew," he said. "She confided in me that Ed had never consummated the marriage, and that as far as she knew, he had no intentions of ever doing so."

"Did she say why?"

"Some odd notion he had that sleeping with her would demean her. He had… some bizarre ideas about sex."

"Yes, I've heard." Lestrade tried to keep the contempt out of his voice. "But he wasn't jealous of who Addie was sleeping with?"

"No," Inglis said readily.

"Wasn't jealous of your friendship with his wife?"

"Not at all. We spent a lot of time together…"

"The two of you? You and Addie?"

"And Ed too, sometimes. In fact, a year ago he told me if he was ever to die, he'd like me to marry Addie and look after her."

Silence. Lestrade mulled this over, not sure of what to say. Let Sherlock think the implications of that one through.

"He was concerned about dying unnaturally, then?" he asked Inglis, unsmiling. "'Cause that's an odd thing to just up and say to someone."

Inglis raised one eyebrow. "Do you happen to have a will, Inspector Lestrade?"

"Yes. And in it, I don't bequeath my girlfriend to anybody."

Dyer suddenly coughed explosively into his fist; Lestrade, irritated that he'd let himself be goaded into childish retorts like that, leaned back in his chair and composed himself for a few seconds. "Unhappy marriage?" he asked finally.

"Oh, quite the opposite. They seemed very happy," Inglis said. "Oh, of course, Ed was a horrible hypochondriac and that kept Addie on the hop. She spent a lot of time nursing his imaginary illnesses. But he seemed to settle down as long as she had some silly 'remedy' to give him that he believed worked."

"And what was that?"

"Various things. Herbs, you know. Homeopathy, that kind of thing. I'm sure Addie once said he thought cancer could be cured with garlic." Inglis sounded disdainful. "The last time I saw them together was when I'd dropped in on Sunday night… Ed had borrowed my camera and I'd come to the house to collect it. They seemed normal. When I came in, Addie was saying that they'd just agreed they wished they were unmarried, so they could have all the fun of getting married again."

"How romantic," Lestrade remarked dryly. "Did you know she was sleeping with Tim Bartlett?"

Another pause. "Yes," was the sulky reply.

Someone's not a happy camper about that state of affairs. "And how did you feel about that?"

"I couldn't have cared less."

"Mycroft's going out to take a look at the Bartlett place tonight," Sherlock was saying, giving half of his attention to John and half to the strawberry milk he was still trying to finish.

"Well, I suppose since you can't get out of here -"

"I want you to go with him."

"Why? The police have already looked there," John objected.

"Why does everyone keep saying that?" Sherlock sounded peevish. "I know the police have already looked there. But haven't we established that they don't really look properly? I'm absolutely sure that the place will yield clues for those who stop and look. And if I were able to get out of this hospital, I'd go and look myself. You know that."

John sighed, leaning back in his chair. "This is going to involve housebreaking, isn't it?"

"It's a locked-up crime scene. Of course it's going to involve forced entry." Sherlock was now searching for something on his phone, though details weren't likely to be forthcoming any time soon. "You needn't worry about the police catching up with you when you're accompanied by the British government. In fact, I imagine it'll be an easy job for both of you."

"Well, that's the other thing. Why does Mycroft need me around?" John folded his arms defensively. "You know he's capable of looking around without my help."

"What sort of a genius," Sherlock wanted to know haughtily, "goes housebreaking without a lookout?"

"About this chloroform…" Dyer was pretending to look over his notes. Lestrade, watching, thought he recognised a few of his own interview gestures and techniques in there, and smiled to himself. "We know it was you who bought it. And where. What I'm curious about is why?"

Inglis glanced away for a few seconds. "I use it in the lab," he explained.

"What lab?"

"I have a lab in my back shed," he said. "I'm an amateur chemist as well as a doctor. That's not illegal. You can come and have a look at everything, if you like. I use chloroform as a solvent, mostly to extract substances from plant matter."

"So you didn't, for example," Lestrade interrupted, "give the chloroform to Addie to use when Edwin demanded his marital rights?"

The young doctor's mouth dropped open. "No!" he exclaimed.

"She said you did."

"Well, she's a liar!"

"Okay," Lestrade said in cool tones. He's certainly doing his best to put her squarely in the dock. Push comes to shove, and this guy would probably accuse anyone and everyone to weasel out of responsibility. "But the fact remains that we know it was you who bought them. Why four little bottles, from four different online sites?"

Inglis looked at him blankly.

"Well, it's just that I checked out the first site last night." Lestrade flicked his pen against the table. "They were selling six litre drums of the stuff. Bargain prices. So why did you buy four 50ml bottles from different retailers? Bit inconvenient, wasn't it? Not to mention more expensive."

"Is that illegal?" Inglis asked in quiet defiance.

"No, but poisoning a man is," Lestrade remarked. "By the way, copping an attitude with me isn't going to do you any favours. I'm two minutes away from cautioning you."

Inglis looked back at him and said nothing - the look of a man who knew the second he opened his mouth, whatever came out was going to be exposed as a lie. Lestrade scribbled down the facts for Sherlock to mull over and changed tactics.

"Okay," he said. "Pretty obvious you're not keen on explaining that. We'll go back to that later. So tell us, how did all four bottles end up at her place, with her prints on them, and Edwin's prints on them, and no evidence at all that you so much as breathed near them?"

"I don't know," Inglis said sullenly. "I suppose she took them. She was at my house a couple of days before the murder. I took her to the laboratory to show her some experiments I was doing on Aconitum -"

"Monkshood?" Dyer broke in.

Inglis nodded.

"That's one god-awful poisonous plant you were playing with, Dr. Inglis," Dyer remarked, and Lestrade bit his tongue. While Jake needed a few lessons on a poker face and an appropriate tone during an interview, he was pretty sharp. Lestrade had no idea what Aconitum was, even if it was called Monkshood.

"Yes, it is," Inglis agreed, a little icily. "But considering neither Ed nor anybody else got poisoned with it, what's that got to do with the price of tea in China? I was showing Addie the extracts I'd got from some of the blooms I'd been working on that week. I didn't watch her the whole time she was in the lab - I was looking into a microscope for part of the time. Maybe she pocketed the chloroform then."

"But you can't say for sure?"

Inglis shook his head. "No. I don't keep a running inventory of my lab - I'm usually the only person in it, and I live alone. But I don't think I remember seeing the chloroform after that day…" He trailed off as there was a sharp knock on the door.

Lestrade, knowing that no one in his team would interrupt an interview in progress unless it was important, bid whoever it was to come in. Sally Donovan opened the door, looking slightly frazzled, one arm outstretched on the handle to hold it open. "Sir…"

"Can this wait, Donovan?"

She shook her head, black ringlets bouncing. "Afraid not, sir. I need to speak with you…" She glanced at Inglis. "In private."

Lestrade also glanced back to Inglis, weighing up whether it would be responsible to leave him uncuffed in Dyer's company. Donovan was still looking at him in mute urgency.

"We'll take five minutes," he muttered to Dyer, then pulled his chair out, stood up and followed Donovan out into the corridor. She'd barely walked him earshot-length away from the interview room door before he changed tones entirely. "What is it?"

"Sir, homicide have just been called in to a residential street address in Enfield," she explained in an agitated staccato. "Neighbours found a man's body garrotted in the kitchen."

"… And?"

"It's Timothy Bartlett, sir."