The team is called in to track down a serial killer after the bodies of multiple women with the same physical description are found scattered across the city. Meanwhile, Maggie juggles her roles as a guardian to Ella and an FBI agent.

When a passenger train is hijacked and rerouted while at high speed with an unarmed OA and Gemma on board, the team races to wrest control away from the unhinged perpetrators and prevent a catastrophe.

When a famous rapper and two teen fans are gunned down on his tour bus, the team discovers there may be more to the story than his feud with another rapper. Meanwhile, Isobel hits a major milestone that has her contemplating her future at the Bureau.