EPISODE NAME : What I Saw (I)
Season : 7
Episode : 15
EPISODE PLOT :
A spate of robberies comes to light after a firehouse lockbox key goes missing; Sergeant Hank Voight suspects a firefighter may be involved, and with Boden's support, he recruits Cruz to go undercover to help sniff out any suspicious activity.
The crossover continues on Chicago P.D. S06E15 Good Men (II).