When a police informant's murder points to the involvement of the notoriously brutal East Jameson gang, the division realizes that cracking this case will not be easy. And when Gail's intimidating mother, Superintendent Elaine Peck, arrives on the scene, there is even more pressure to solve the case. Meanwhile, Andy finds herself paired with Detective Rosati, whose unintentional disclosure of a secret puts Andy's relationship with Luke in jeopardy. And Gail, stressed out by her mother's presence in the station, is assigned to protect the only known witness to the crime -- a seemingly homeless eight-year-old boy with a shocking secret of his own.