In the season 2 Chicago Fire/Chicago P.D. cross over episode, Cruz's brother is asked to wear a wire to get a confession from a gang boss.

Season 2 Episode 9 'You Will Hurt Him'
Dawson and Casey's romance escalates. A broken Shay contemplates suicide and Severide asks Dawson to help her. Joe's younger brother Leon helps Voight's Intelligence Unit imprison the new leader of his former gang for killing a young girl. Mills learns that he has a place at the Police Academy. Boden gets a visit from McLeod, who has found a way to close 51.

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