The manhunt for a serial bomber begins in the upcoming premiere episode, titled "Folie a Deux," of the fifth season of the American procedural drama "Elementary."

After six years of being idle, a serial bomber reappears to wreak havoc again. Watson (Lucy Liu) and Holmes (Jonny Lee Miller) decide to join the NYPD in the manhunt for the serial bomber. Watson turns to Shinwell (Nelsan Ellis) for help. Apparently, Shinwell is Watson's former patient whom she saved when she was still a surgeon. Meanwhile, Holmes realizes that Watson may no longer feel fulfilled with her detective career so he confronts her about it.

The promo trailer for "Folie a Deux" shows Holmes and Watson looking at details on the newest case. The partners in crime have revealed the possible character of the criminal. Holmes thinks that the serial bomber is not the kind who is driven by revenge rather by his passion in making things go bad. Watson, on the other hand, thinks that the criminal maybe just wants his or her act to land on the front pages.

In one of the sneak previews, Holmes asks Watson what is it that makes her proud of an ex-convict like Shinwell. Watson explains that she is not particularly proud of him but of the work the surgical work she did on him. She then retells the near-death surgery in detail, which Holmes thinks made her miss being a doctor than being a detective.

Regarding Holmes' fear of Watson's disinterest in their detective work, executive producer Rob Doherty revealed about this on Entertainment Weekly.

He said, "Joan makes it clear that she's quite happy being a detective, but at the same time she misses helping people. It's something that she could do when she was a surgeon, it's something she could do when she was a sober companion, but, as she says in the first episode, she and Sherlock are in the punishment business."

"Elementary" season 5 premieres Sunday, Oct. 2, at 10 p.m. on CBS.