A Little Devil Complex (II) - S2.E13

Antonio and his sister Gabriela go to the office of Elliot Gish, the man they believe started the fire that killed Shay. Intelligence, along with patrol officers Burgess and Roman, put pressure on Gish to confess. Lindsay approaches Voight about returning to Intelligence when she realizes that the task force isn’t what she thought it would be. Desk Sgt. Platt has everyone curious why she’s being overly cheery, friendly and nice.

The crossover starts on Chicago Fire S03E13 Three Bells (I).