S05E18: Purgatory

Distraught over losing an appeal to her suspension, Sasha gets into a car accident that claims the life of a young child; Sully and Ty take the L.S.A.T.; tensions flare between the cops and the firefighters when Maritza goes after J.D., the newbie firefighter, who turns out to be an ex-cop who ratted out Maritza's former partner for stealing drug money; Faith and Fred are still at odds over her return to work; Walsh is promoted to lieutenant; Ty watches over a devastated Sasha, who's racked with guilt over the car accident, Doc's shooting spree, and the events surrounding the deaths of Tanzi and Nardo; J.D. gives Faith and Bosco important evidence he discovered as he put out the fire resulting from Sasha's car accident, which leads the cops to uncovering the basis for the accident and exonerating Sasha.