Sherlock and Joan look into the murder of a former organized crime group member in tonight’s installment of “Elementary.”

According to the synopsis for Season 6, episode 6 of the CBS series, Sherlock (Jonny Lee Miller) and Joan (Lucy Liu) are drawn into the world of nuclear security when they investigate the murder of an ex-Yakuza gang member.

In the promo for the episode, Sherlock tells Joan and Marcus (Jon Michael Hill) that the killer took something away from the victim, revealing that the latter actually had a flash drive hidden in his prosthetic finger.

In a sneak peek from the episode, Sherlock informs Joan that the Tokyo Police has finally got back to him about their queries concerning the victim, Ando Azuma.

“Inspector Natsu was enormously helpful. We just had a bad connection,” Sherlock says. “He consulted an informant and confirmed that after 10 years of faithful service Ando Azuma retired from the Yakuza, sliced off his pinky — his exit fee — and swore to never again engage in criminal activity. Now, a Yakuza who retired with honor as Ando did is generally left in peace, so the inspector was surprised to hear that he’d been murdered.”

Joan, on the other hand, thinks that Ando’s murder isn’t surprising. “He could have killed by a rival gang member,” the former surgeon says. “You don’t spend 10 years in organized crime without making some enemies.”

Though Natsu is shocked by Ando’s murder, the inspector had a theory of what led to the victim’s death. “It turns out Ando was not your typical Yakuza thug,” Sherlock says. “[According to Natsu, Ando] was a specialist in industrial espionage and blackmail.”

“So that hidden flash drive that you and Marcus found out about, he could have had blackmail material on it [that ultimately ended his life],” Joan presumes.

Elsewhere in the episode, Captain Gregson (Aidan Quinn) is blindsided by a stunning personal confession from his daughter, Hannah (Liza J. Bennet).

As revealed in another sneak peek from the episode, Gregson finds out that Hannah is an alcoholic. “Hannah came to see me last night and told me that she’s an alcoholic,” Gregson tells Joan.

In an attempt to comfort Gregson, Joan tells him that Hannah opening up to him about her addiction is actually a good thing. “It means that she knows that she needs help and that she wants your support. Those were important steps towards her recovery,” Joan says.

“I missed all the signs,” Gregson admits. “That’s why I wanted to talk to you. You’re a sober companion. I wanna do the right thing by Hannah. Tell me what I need to do.”

“Elementary” Season 6, episode 6, titled “Give Me the Finger,” airs Monday, June 4 at 10 p.m. EDT on CBS.