Lucy Liu as Joan Watson
A sneak peek to “Elementary” Season 5, Episode 1 shows Joan’s (Lucy Liu) reunion with her former patient Shinwell Johnson (Nelson Ellis). CBS

Shinwell Johnson (Nelson Ellis) may hold the key to solving a bombing case in Season 5, episode 1 of “Elementary.”

In a newly released sneak peek at the season premiere, titled “Folie a Deux,” Joan Watson (Lucy Liu) reunites with her former patient Shinwell and asks him about Nathan Resor (Matthew Del Negro) — a person of interest in a case about a serial bomber who becomes active again after being dormant for six years.

“I wanted to ask you about someone who was at Great Meadow the same time you were, Nathan Resor,” Joan tells Shinwell, whose life she saved when she was a surgeon. “I saw in his file that the two of you worked together in the prison cafeteria.”

Although Shinwell admits that he remembers Nathan, he tells Joan that he doesn’t know him that well. When asked if he said anything to Nathan about the Bensonhurst bomber, Shinwell says, “Not to me.”

While Joan doesn’t get much helpful information from Shinwell during the meeting, the ex-convict may not be ready yet to disclose what he knows. Whether or not that’s the case, the two will definitely meet again, as TVLine reported last month that Ellis is set to appear in at least two more episodes after the premiere.

In an interview with Entertainment Weekly earlier this month, “Elementary” executive producer Rob Doherty said that Season 5 will open with Sherlock Holmes (Jonny Lee Miller) sensing that Joan is no longer as enthusiastic about her work as an investigator as she’s been in the past.

While Joan will make it clear that she remains “quite happy” being a detective, Doherty said that the former doctor will admit that “she misses helping people.”

Fortunately, it won’t be long before Sherlock finds a way for Joan to continue her work as a detective while doing the kind of helping she has always wanted to do.

Doherty revealed to Entertainment Weekly that Sherlock will convince Joan to assist Shinwell as he transitions from prison life back to the outside world.

“He is someone with a dark and troubled past, who is trying to reform himself, but he brings a lot of baggage to our doorstep,” Doherty said of Shinwell, who is a character created by Sherlock Holmes author Sir Arthur Conan Doyle in his 1924 short story, “The Illustrious Client.”

Doherty, however, noted that “there may be a difference of opinion” between Sherlock and Joan along the way regarding whether keeping Shinwell in their orbit is a good idea.

“Elementary” Season 5 premieres Sunday, Oct. 2, at 10/9c on CBS.