A social media influencer party ends with the brutal murder of a popular guest. Chris Park's side hustle makes him uniquely qualified to lead the CSI team in their investigation.

Truck and squad are called to aid in a massive all-city response when an old, ill-equipped factory-turned live/work space quickly turns into a firestorm, trapping countless unsuspecting victims. The dire situation quickly turns personal when it is discovered that one of Chicago PD's own has a family member at the scene. The crossover continues on Chicago P.D. S04E016 Emotional Proximity (II) and Chicago Justice S01E01 Fake (III).

Olinsky's daughter remains in critical condition following a massive fire - leaving Intelligence on edge, but more determined than ever to track down the suspect. Voight opens up the case, knowing that he has Stone and his team's full support in the investigation, and all of Firehouse 51 behind him to examine potential origins of the fire. The crossover starts on Chicago Fire S05E15 Deathtrap (I). It continues on Chicago Justice S01E01 Fake (III).

Firehouse 51 responded to a horrific warehouse fire that killed 39 people. This led the Chicago P.D. on a manhunt for the suspect. Now with someone in custody for both arson and multiple murders, it is up to Peter Stone and his team, including lead investigator Antonio Dawson to step in to bring some peace and resolution to so many families and friends of those lost - including one very close to home. The crossover starts on Chicago Fire S05E15 Deathtrap (I) and Chicago P.D. S04E016 Emotional Proximity (II).

It's a miracle when a trauma patient survives the trip to the hospital, putting the pressure on Dr. Rhodes to keep the man alive. Dr. Choi and Dr. Manning have difficulty diagnosing the location of infection in a paralyzed patient. Dr. Reese must find purpose for a grieving widower who relies on a superhero costume. Meanwhile, April pushes Dr. Halstead to use unproved medications to help a patient with no other options.

When a turf war escalates, members of truck and squad find themselves caught in the middle as unsuspecting hostages when a group of armed gang members take cover and assume control over Firehouse 51.