Sherlock and Joan investigate the murder of her former psychologist in next week’s episode of “Elementary.”

In a sneak peek from Season 6, episode 4 of the CBS series, Sherlock (Jonny Lee Miller), Joan (Lucy Liu), Marcus (Jon Michael Hill), and Captain Gregson (Aidan Quinn) conduct an initial investigation on the victim’s body at the crime scene.

“Victim’s a therapist,” says Gregson. “Cleaning lady found the body a few hours ago. Assuming she finally stopped screaming, she’s at the precinct giving a statement right now.”

When Sherlock wonders how much of the victim’s blood volume is on display, Marcus replies, “Over 50 stab wounds worth based on preliminary account.” Marcus adds that the murder weapon hasn’t turned up yet, thinking that the killer took it with him when he left the therapist’s office.

Marcus also notes that there’s no sign of a break-in. “To get into the building you got to punch in a code,” the NYPD detective explains. “The killer either knew it or slipped in with someone who did. Before you ask about security cameras, this place doesn’t have any. The doctors here need to protect patient confidentiality.”

Since there’s a lot of blood all over the victim’s office, Joan says that “the murder itself seems frenzied like whoever did it was in a rage.”

“So we could be looking for an unstable violent individual who is fixated on the victim, a psychiatrist,” Sherlock says. Though the majority of mentally ill people has no history of violence, the British sleuth thinks that the victim’s killer is one of her patients.

When Marcus comments that the victim’s dozens of patients make for a big suspect pool, Joan says that she can narrow it down by one. “This is Dr. Candace Reid, she used to be my therapist,” the former surgeon reveals.

Meanwhile, Joan mulls over a huge life change while working on the case. According to the synopsis for the hour, Joan considers making a major life change after she gets to read her own therapy file.

Elsewhere in the installment, Joan tells Sherlock that she wants to meet his new friend, Michael (Desmond Harrington).

“When are you going to introduce me to him?” Joan asks Sherlock in another sneak peek from the next episode.

“You’re asking as if he and I were a couple,” Sherlock replies. “We’re fellow in a recovery program.”

When Joan says that “it would be nice to put a face to the name,” Sherlock says that she can join him when he delivers a progress report to him about Polly Kenner, the missing woman Michael asked Sherlock to look for.

“Elementary” Season 6, episode 4, titled “Our Times Is Up,” airs on Monday, May 21 at 10 p.m. EDT on CBS.