'Criminal Minds' season 11 spoilers: BAU investigates Boston massacre in episode 12

A killer is stalking the streets of Boston in the upcoming episode of "Criminal Minds."Facebook/CBS

The Behavioral Analysis Unit (BAU) heads to Boston to solve a string of murders in the upcoming episode of the CBS series "Criminal Minds."

In "Drive," CarterMatt reports that the unit will be tapped to track down the killer who prowls the streets of Boston. The bodies of his preys end up being discovered in public places. Upon preliminary investigation, BAU discovers that all victims used a specific taxi or ride sharing service before their tragic deaths. The team has reasons to believe that following its trail will lead them straight to the murderer. Will they be able to apprehend him before he strikes again?

Last episode, viewers saw the return of BAU's resident genius, Reid (Matthew Gray Gubler). He was sent by the team on a blind date, which turned out to be a trap to apprehend one of the Dirty Dozens, Ms. 45 (Aubrey Plaza). The set up quickly changed from bad to worse when the brunette told Reid she knew that the entire thing was a set up by the FBI. She challenged him in a game of wit. If he was able to answer perfectly, she would surrender. If not, Reid and his team, which was monitoring from a post, would have to let her go.

Ms. 45 asked Reid about his mother. It turned out that when he took a break from BAU, he was with her. His mother was suffering from Alzheimer's, and chances were he had it, too. The woman then revealed that she was not alone. Another member of the group, codename Bomber, was with her and she had set up an explosive enough to destroy the entire block. If Reid would not let her go, they would blow the whole place down. The BAU told Reid to do as she commanded, but he had an ace in the hole.

Reid told Ms. 45 that he found her father, the reason why her life turned into shambles. He killed her mom, but managed to escape capture of the police. Reid said her old man, already homeless, was just outside. If she triggered the bomb remote, she would never know where he was. Reid then tricked Kat, saying that they already had her father, when in fact, they still did not know where he was. At the end, BAU apprehended Ms. 45, Bomber, and the rest of the Dirty Dozen members.

"Criminal Minds" season 11 airs Wednesdays at 9 p.m. EST on CBS.