Lestrade wonders how he's even been roped into this. So it is for a case, if a case exists in the first place. In his opinion, the suspect could just be a bloody awful shrink – that's why an higher percentage than usual of his patients are dead. Instead someone's sister refused to accept the obvious truth and dangled before Sherlock the chance of a serial killer acting as a shrink and mind-fucking people to death (devious hypnotism, she supposed...Lestrade suspects too much Curse of the Jade Scorpion or something similar on her part). Of course Sherlock took to the case like a fish to water, and booked a few sessions with the man. If he'd been informed then, Lestrade might even have encouraged his consultant – a shrink, even an awful one, looks like something Sherlock would profit from.
But then the man suggested a group session with his family, and that's when Lestrade is supposed to help. He can't fault the detective for not wanting to get his parents involved into the mess, but acting as a stand-in dad will be a nightmare, he already knows. Not to mention it's just weird having Mrs. Hudson here. Martha, he has to remember to call her Martha if they're to be married (and who is Sherlock supposed to look like anyway? Some uncle?). That mystery series his ex liked (with a bit of romance and just enough humour to make it tolerable when he was bored enough) can have whatever in it, it'd be too weird calling his wife by last name.
Dr. Simpson looks like an average bloke, chestnut hair and big glasses, but Lestrade (Greg Holmes, now) knows better than to judge a book by his cover. He apparently likes to make things difficult for the DI. Well, not a DI anymore now, by Sherlock's instruction, not to be intimidating; still a policeman though, because he wouldn't know how to be anything else. Because he suggests starting the session without his patient (and what kind of session is that?) to obtain a bit of information without conflict in the air, and how is Lestrade supposed to improvise without the detective there to take cues from? He's not a bloody actor. He can't protest, though. Sherlock probably feels like the nonexistent God gifted him with snooping time, and won't take kindly to Lestrade trying to stop him.
So he and Martha (Martha, Martha, Martha) face the doctor together. Not that it's dangerous. He trusts his pretend son enough to know he won't send her unprepared against danger.
“Please take a seat,” the man says. There are four in a half-circle, and instinctively they leave the most central one for Sherlock (when...no, if he'll join them) and flank it on both sides.
“This choice is meaningful,” Simpson remarks. “I've ascertained your son's quite...peculiar attitude towards feelings. And one of the questions I needed to ask is to what degree he's witnessed or experienced positive feelings' demonstration. So? Any reason for you both to keep distance?”
“Look, I've come to help if I can, not to be told it's my fault Sherlock's weird...” the policeman grumbles. This man is really shit at his job.
“Honestly, dear, I thought it'd be obvious that we aren't cold to each other, much less our boy. We just sat like that so when he comes he'll be just in front of you – like he should be – and have us both near. That's not being distant, it's having our priorities straight, isn't it?” Mrs. Hudson says – gently, politely, but with a harsh undertone worthy of her 'son' when put in Anderson's proximity.
Before the man can answer, Lestrade adds, “Not to mention you'd nitpick about which one was closer to him otherwise, wouldn't you?”. The admiring, completely honest smile he sends her way might be bordering enamoured enough to make any lingering doubts about their marriage or its status melt away.
Simpson doesn't reply, he just smiles the neutral smile of every shrink on the globe and nods accepting their point.
“So you both feel like you need to protect your son still? From who, pray tell? And why not allow him beside his brother?” he queries.
“Where do you see Mycroft, dear? I'm getting a bit concerned, really,” Martha wonders. Because of course the I-hate-legwork British Government had no time for this. Sherlock didn't even ask, in all likelihood.
“I assumed he was just slightly late,” the doctor replies.
“Nah, he's too busy with work...and you should know the saying about people assuming,” Greg says, ending with a chuckle and liking his ' I'm the biggest git in the world's father, why be ultra-polite?' charade.
Simpson coughs the embarrassment away, while Mrs. Hudson sharply and quietly calls, “Love!”. Well, better than what the ex-wife did when he displeased her at some gathering.
“Too busy to be supportive of his brother?” Simpson tries to be cold, inquiring facts, but man, is he annoying!
Martha and Greg act as one there, really like an old married couple. They laugh (because really, the problem is how to keep Mycroft out of anyone's life, much less Sherlock's) and – together- they move the extra chair behind the one meant for the sleuth.
“They do quarrell all the time...” Mrs. Hudson acknowledges.
“...but Mycroft will always, always have his little brother's back; he did since Sherlock's born,” Lestrade ends for her. Then he starts wondering if Sherlock wanted to pass for a total outcast so he could attract a murderous interest. Well, that's what the detective gets for not giving clearer instructions firsthand.
“One last question before calling your son in,” the doctor says, turning towards Greg, “I've been informed you're a policeman. Is it your habit to bring work home? Can you honestly say your professional worries did not spark or boost Sherlock's most morbid's tendencies?”
Which were two questions, technically, but Lestrade supposes he deserves being accused after irritating the man (who is highly unprofessional, this is sure...but it isn't enough to say he's murderous).
“I always tried not to do that,” Lestrade answers, and it's honest. Just not with this family, or with children – he didn't have any. “And believe me, he doesn't need any encouragement to be morbid.” He chuckles again.
“And he's not really morbid,” Martha argues. “He might look like that, sure, but I always maintained morbidity depended more from one's frame of mind than from one's actions. Doctors play with blood and body parts all the time, but nobody calls them morbid on the whole. And Sherlock's attitude has always been more scientific than anything else. It's not the degree that makes the scientist.”
Greg almost objects, but the woman needs that notion if she's to live in the same house as Sherlock, he guesses.
“Thank you,” the doctor concludes “I'm going to call Sherlock in now.”
“He gets easily antsy, but I'm sure you know. Just don't get angry if you don't find him right out the door – moving helps him,” Lestrade remarks, terrified of what might happen if the man finds the detective snooping around.
“I'll keep it in mind.” With that, the shrink leaves them alone.
The doctor just left the room, when Mrs. Hudson (gloved...well, it's winter) hands move to snatch the two block-notes left on the desk. Lestrade's eyebrow shoots very, very up. The lady probably tolerates her tenant a lot less than everyone thinks, and instead honestly enjoys his company.
Martha sends him a talking, mischievous look, that says ' he's searching for Sherlock anyway' and ' this man is a suspect' and ' I'm not contaminating the evidence, so why not?'. The DI really should protest and follow the rules, but he's never been too good at that himself.
In the next couple of seconds it's clear that Simpson is indeed guilty. The gray block-note the doctor wrote in during their session is perfectly normal. The black one, though, has happy emoticons near creepy comments about people, and Lestrade recognizes at least one name (the one whose sister brought the case).
Since he has good reason to investigate, now, he starts opening cupboards and finds ulterior proof of wrongdoings. Every doctor the DI knew kept around a little bit of everything (mostly freebies), but Simpson has a lot of a single drug. Either he really slips it to unaware patients, or he sells it, but something’s definitely fishy there. Of course, at the time he isn't aware that this specific drug heightens suggestibility and lowers inhibitions, but he doesn't need to know it.
When Simpson comes in, Sherlock in tow, he behaves quite stupidly. Honestly, playing the shocked/outraged card? Yelling, “What's happening here?” isn't going to deter anyone. The man doesn't even try to flee. Not that Sherlock or Lestrade would let him. He tries to take his possessions back from Mrs. Hudson, but he's cuffed by the DI before he can even touch her. Hey, he's sparing the bloke a few broken bones.
Lestrade informs his prisoner of his rights and the suspicions pending over him, then starts calling his subordinates. The man quieted down, looking like he's trying to come up with a strategy. Bit late for that.
In the meantime, half a look gave Sherlock all he needs to know. Lestrade has to fight down a laugh hearing Mrs. Hudson apologize, saying that she didn't mean to steal the case, and “it's not your fault he wouldn't leave a patient alone, dear.” Personally, the Inspector wishes to bark, “don't pout now,” at his consultant...but someone has to at least pretend to be serious when they have a murderer (probably a serial killer) here. He'll let Sherlock have a private interview with Simpson later, so the detective can glean all the details he's interested in. Hopefully that will be enough. If they have ruined the case for Sherlock, there will be a very unamused John to deal with later.