February 2020 Chicago crossover event

Ambulance 61 is dispatched to a call, when they arrive they find multiple people down of suspected opioid overdoses. Squad 3 responds to assist when one of the victims is trapped. One of the victims boyfriend, Travis Butler, shows up but runs when questions start being asked. The Intelligence Unit starts investigating where the drugs came from and it is found all the victims have suffered from counterfeit Oxy. Casey offers to take Brett to meet her birth mom if she wants a friend to go along. Intelligence tracks down the boyfriend who agrees to help the police. Former Chicago P.D. officer Sean Roman shows up at Firehouse 51 looking for his sister Sarah, who was friends with the original victims, and went missing a week prior. Boden, Severide, Casey, Brett, Foster, along with Roman begin putting the pieces together. Boden tells his wife Donna, who is a teacher at the victims school, about the deaths who takes it hard. Brett takes Casey up on the offer and they go to meet her birth mother. Donna gets Severide and Roman a meeting with Sarah's best friend who points them to Sarah's boyfriend, Logan Peters. When Brett goes to the door of the address she was given she is told no one by that name lives there. Roman and Severide visit one of Roman's old connections from his days on the street. The two get held at gunpoint but take control of the situation and are pointed to where Peters spends time. After things begin to get dangerous Severide asks Roman to go to the police, when he refuses Severide refuses to continue with him and goes to Intelligence on his own who are all shocked by the news he's in Chicago. The next morning Brett's birth mother shows up at Firehouse 51, the two begin talking and her mother reveals that she is pregnant. Their meeting is cut short when the firehouse is dispatched to a house fire. Upon arrival shots are fired toward the first responders and Roman comes running out of the house. Roman informs them that Peters is inside the house and was firing at him. Casey and Severide go inside to search the house and find Butler suffering from a gunshot wound. Intelligence shows up at the scene of the house fire.

Neighbors identify Butler heading inside the house with a can of gasoline and is assumed to have started the fire. Roman reveals to Burgess that his sister has been dealing for Peters. Halstead and Upton head to the hospital to interview Butler where a fight breaks out between Butler's father and victims parents of the fire. Butler tells Intelligence that Peters is responsible for Sarah going missing. Burgess and Roman interview Peters' ex-roommates who identifies Sarah and points them to a lake house. At the lake house they find Sarah frozen to death under snow in the back yard. Roman visits his parents and he informs them that they found Sarah's body. DNA found under Sarah's fingernails matched to Peters. Running location history Intelligence tracked suspects history to a warehouse where Peters is found dead. Ruzek and Burgess talk through their feelings after losing the baby. A witness near the warehouse at the time of Peters murder identifies a black Range Rover driving away from the scene that points Intelligence towards a house where they find another suspect. Camera feeds reveal a blue Nissan driving away from the warehouse at the same time. Burgess re-questions the witness who identified the Range Rover but he doesn't recall seeing a blue Nissan. Platt finds out that the witness used to also be a former confidential informant of Roman's. Burgess also finds that Roman's cousin drives a blue Nissan. With signs of Peters murder pointing towards Roman, Burgess confronts him but he continues to say he had no involvement. Voight orders Intelligence to bring in the witness but he's cleared out his apartment. His landlady however tells Intelligence that he paid off his debt of three grand, Voight suggests pulling cameras from the bank to see who paid off the witness. Members of District 21 and Firehouse 51 attend Sarah's funeral. Following the funeral service Roman prepares to be taken in for murder but Voight looks the other way and lets him off the hook.

Jessica Lerner with TV Fanatic who reviewed the first part of the crossover stated that "the episode gets an 'A' for effort, but a 'B−' at best in execution" noting that Chicago Fire usually follows a serialized format while Chicago P.D. follows a procedural format making the two series incompatible.[7] Lerner later mentions that she enjoyed the unusual pairings between characters Kelly Severide and Sean Roman because of their similarities and said that overall this crossover event was disappointing compared to the previous one.[7] Lizzy Buczak also with TV Fanatic reviewed the second portion of the crossover also found the event compared to the previous one but said "it found a way to bring these two squads back together again."[8] Bryna Kramer with the Meet Us at Molly's podcast stated that she "thought it was fine," but felt like "it was a little overhyped." Gina Zippilli, also with Meet Us at Molly's, said that she "liked it," but "Roman definitely grated on [her] the same way he did when he was a regular."

Chicago Fire, the first part of the crossover event, was viewed by 8.66 million viewers. Meanwhile, during the second part of the crossover Chicago P.D. brought in 8.12 million viewers.[9]