The episode begins at Molly’s where Herrmann asks Otis for a camera because his wife wants to make a video journal for the baby who is due in a couple of weeks. Otis tells him to use the camera on his phone. Otis is organizing a ladies night special at Molly’s and Dawson is slightly surprised. Actually she doesn’t like the idea. Casey is still trying to cope with Hallie’s death. Shay tells Dawson that her cycles are delayed. She tells her that she hasn’t taken the home test because they are never hundred percent. So, she and Kelly went to the doctor and she will know the results later. Mills arrives and it is clear that Dawson and Mills still aren’t talking.
Shay tells Dawson that it is crazy that Mills if Mills cannot forgive her because she (Dawson) was only trying to protect him. Herrmann arrives and gives Kelly a pregnancy pillow. He tells Kelly to give it to Shay when the time comes. At that moment, the crew gets called to structure a fire at the Cook County prison. Boden talks to the warden and tells Casey to go inside with a small team. Casey tells Mills, who looks nervous, to ignore the inmates. Lucci, one of cops, takes the team inside. Boden radios Herrmann and tells him that Cindy has gone into labor. He tells him that he can send someone to pull him out. Herrmann tells him that he is fine. He decides to stay with the team and put out the fire. The team locates the fire and they go inside to put it out. They also find that an inmate, Randall, has been stabbed. They quickly pull him out and Casey informs Boden. Boden sends Shay and Dawson to check on the inmate. Dawson puts pressure on the wound but Randall doesn’t feel the pain. Shay goes to get a stair chair. She tells Mills to stay with Dawson. The team manages to put out the fire.
They are about to leave when the power goes out and they all get stuck inside. The team gets locked inside with some dangerous inmates. Boden is worried. Shay is about to go back inside with a stretcher, but Boden stops her. He asks the warden about the backup generators. The warden tells him that the system shuts on its own, and it will reset in a while. Boden tells the warden to give him the blueprints of the prison because he needs to find a way out for his guys. Later, the warden tells Boden that all exit points of the cell are remotely operated and they need power to open them up. Boden doesn’t want to wait any longer. He tells Kelly to go in with the emergency response team and get the guys out.
On his way, Kelly learns that the test results are negative; Shay is not pregnant. Inside, Dawson decides to do an emergency procedure on Randall. Kelly cuts open the first door. Herrmann radios Boden and asks him if there is any update on Cindy. Shay calls the hospital to check. Casey tells Boden that there is another fire somewhere in the prison. He tells Boden that the fire could be electrical which is stopping the grid from resetting. Lucci sees that one of the prison guards is nowhere to be found, and the inmates are roaming freely around the prison. On the outside, Shay tells Boden that the doctors need to perform an emergency C-section on Cindy. Boden decides to withhold this information for the moment. He then sends Otis and Mouch to the substation. Inside, Lacey and Herrmann find a dead body locked up in one of the cells.
It is Corbett, the guard who went missing. They also learn that his keys are missing and they realize that the inmates have taken the keys. Lacey informs Boden about the situation. Lucci manages to retrieve the keys but one of them pulls out a knife and takes Herrmann hostage. Lucci is furious but Casey tries to keep everyone calm. Dawson and Mills have a heart-to-heart. Dawson wants to put everything behind and start afresh. Mills tells her that they can have a fresh start if she admits that she has no feelings for Casey. They are interrupted by Kelly, who is trying to cut open the door. Lacey asks Lucci if there is any place where they can move these inmates. Lucci suggests the chapel. Casey tells Boden that they are moving the inmates to the chapel. Kelly manages to cut open the door and Shay rushes in with the stretcher.
Boden is happy that they could rescue the wounded inmate. Mills wants Dawson to answer his question. She admits that she has feelings for Casey. Inside the chapel, Casey offers to switch places with Herrmann. The prisoner tells Casey that he doesn’t want him, he wants Lucci. He is the one who killed Corbett, and now he wants to kill Lucci. Casey tells Lucci to reason with the inmate. Lucci tells him that these inmates are animals who don’t like their zookeeper. Kelly manages to locate the prison engineer and puts him on the radio to talk Mouch and Otis through an electrical reset. Kelly informs Casey about the recent development. Boden radios Casey. He has a message for Herrmann. Shay tells Herrmann that Cindy gave birth to a baby boy. Herrmann uses this distraction to free himself from the hostage situation.
A riot breaks out, but the officers manage to get inside an office. Casey instructs Kelly to find the supply duct to the chapel and also find the smoke damper. He then tells Kelly to break the damper manually. He then tells Otis and Mouch to get the power back on as soon as possible so that the fans could start blowing the smoke into the chapel. The plan works and the inmates have a tough dealing with all that smoke. The team manages to escape from the office with Lucci. Herrmann receives a call from the hospital. The baby is not doing too well. He rushes to meet his wife and son. By the time he arrives at the hospital, everything is under control. He is relieved to see that his wife and son are fine. Later, Boden tells Mills that the higher-ups haven’t promoted him to the squad.
Mills is tired of all the politics. He walks out. Cindy tells Kelly and Shay that she wants them to be their son’s godparents. Kelly and Shay are delighted. Next, Otis learns that a sports bar is being built next to Molly’s. Mills goes and enrolls himself in the police department. Dawson goes to Casey’s house to reveal her true feelings. The whole house is a mess. Casey has still not gotten over Hallie’s death. Elsewhere, Shay and Kelly run into Renee. She tells Kelly that she is pregnant with his baby. Kelly is at a loss for words. He hugs Renee. Shay stands there, watching them. The episode ends at this point.