While responding to a call involving a victim incapacitated with a leg wound, Sylvie Brett witnesses a murder and is threatened by the shooter not to go to the police. Unsure of what to do, she tries to track down Antonio from Chicago PD. Elsewhere, Firehouse 51 jumps into action when a fire breaks out inside a restaurant, trapping several people inside a vault. Meanwhile, with his wedding day to Trudy fast approaching, a nervous Mouch starts to get cold feet.