Dermot Mulroney and Tracy SpiridakosPeter Gordon/NBC Tap Here To Add Us Weekly As A Trusted Source Add as a preferred source on Google The worlds of Chicago Med, Chicago Fire and Chicago P.D. are set to collide in an epic One Chicago crossover - and no one is safe. Chicago P.D. showrunner Gwen Sigan exclusively told Us Weekly on Tuesday, March 3, that unlike crossovers past, the Wednesday, March 4, mashup will focus on one incident that "continues throughout the three hours." As a result, "You see pieces keep coming back, and characters keep coming back.