An arsonist targets Lt. Severide. Meanwhile, Station 51 is under scrutiny by Gail McLeod, a financial consultant for the city who is deciding if any firehouses should be closed. Mouch receives a visit from his Japanese girlfriend, Lt. Casey "celebrates the one-year anniversary of Andy's death, and Shay suspects Severide's paternity.

In the wake of Heather's incident, Lt. Casey is having a hard time handling his newfound responsibilities. Lt. Severide is on edge dreading the next attack from the firehouse's arsonist. Meanwhile, with Renee back from her mother's, Severide knows he has to confront her about his paternity suspicions. Elsewhere, Mouch begins his campaign for union president and Shay and Dawson feel that they need to get out more.

Lt. Severide has his strong ideas on who the serial arsonist is, but first needs to find proof to back up his suspicions. Meanwhile, Lt. Casey adjusts to his new lifestyle in the wake of recent events and Molly's bar is failing, much to the dismay of owners Hermann, Dawson and Otis. Elsewhere, Dawson goes out on a date with Jay Halstead, one of the bar regulars, and Mouch's campaign trail starts to get on track with the aid of Isabella, an old friend of Dawson's.

Lieutenant Severide is anxious to implicate the serial arsonist, while Dawson and Shay get a shock on a routine call. Meanwhile, suspicions continue to point to Clarke as the mole inside the firehouse and Molly's falls deeper into the red. Elsewhere, Mouch campaigns for union president, with the aid of Isabella, and Boden butts heads with Gail McLeod.

While out on a jog, Severide comes across a secluded and empty construction site and encounters a young boy who has been trapped in a backhoe loader and is in dire need of assistance. Boden and McLeod continue to butt heads about the future of the firehouse and Boden breaks news about his future to Casey. Meanwhile, it's election day for the union presidency and Mouch and Greg Sullivan have a debate on Otis' podcast. With rival bar Game Day's future in peril, the finger is being pointed at Molly's.

El equipo de bomberos está en la escena de un accidente grave que implica un carro petrolero y un tren que luego se estrelló contra un almacén.

Cruz y su hermano se llenan de emociones cuando una joven recibe un disparo en su vecindario. Mientras tanto, la pelea entre el Director Boden y McLeod se intensifica.

Chief Boden prepares to counterattack McLeod in a final effort to save the firehouse from closure and the romance between Dawson and Casey escalates. Leon is making progress in the gang murder investigation, but Cruz cannot stand being left in the dark by Voight, fearing for his brother's safety. Meanwhile, Severide and Katie bond to make up for lost time and Otis feels uncomfortable living with Severide and Shay after Devon's latest escapade.

Boden y el equipo se preparan para luchar contra la decisión de cerrar Firehouse 51. Mientras tanto, el peligro crece mientras el equipo responde a una llamada de emergencia en un edificio de apartamentos.

Casey vuelve a trabajar al Destacamento 51 después de casi encontrar la muerte en el derrumbe de un edificio y Shay se encuentra con Allison Rafferty, su nueva compañera, que es simpática con todos excepto con ella.

El teniente Casey trata de convencerse a sí mismo y a todos los que lo rodean que está sanísimo luego del incidente en donde casi pierde la vida en cumplimiento del deber.

Cuando un automovilista ebrio choca contra un transformador, todo el barrio queda sin luz una noche helada de invierno en Chicago y los integrantes del Destacamento 51 salen a prestar su muy necesitada ayuda.

Severide se siente excluido durante la búsqueda de su hermana desaparecida. Mientras tanto, Shay consigue una pista sorprendente; Casey recolecta nueva información acerca de su lesión en la cabeza y Dawson se entrena para la prueba física de la Academia.

Severide se siente frustrado cuando Vince Keeler queda en libertad, pero mantiene la esperanza de que la justicia prevalecerá.

Lt. Severide hits the top of the list as Det. Lindsay starts calling in suspects with the clearest motives to make the guy who kidnapped Katie disappear. Meanwhile, Jones is still having trouble fitting in as word of her disruptions reach the fire department’s headquarters. Elsewhere, Herrmann celebrates his twentieth anniversary with his wife, but no one supports his idea on the gift he intends to give.

Lt. Severide is reminded of his own past by a man he saves from a car accident and feels compelled to help him. Elsewhere, Lt. Casey and Chief Boden grapple with how to dock Jones per her father’s orders. Meanwhile, Mouch and Dawson have troubles with the opposite sex and an emotional call to duty creates ripples throughout Firehouse 51.

Lt. Severide sticks his neck out for Dave Bloom, a fellow firefighter from Denver who is troubled by addiction. Elsewhere, Dawson and Shay leave town for a "girl's weekend" at a cabin in the woods. Meanwhile Jones struggles with the knowledge that her father is pressuring Chief Boden about her career path and Mouch's internet dating profile gets an upgrade with the help of Mills and the guys.

A suicide note is delivered to a surprised Dawson and Lt. Severide digs deeper into Bloom’s dark past. Elsewhere, Chief Boden learns shocking news, and with the help of Shay, Lt. Casey goes on the search for a life-changing item.

Lt. Casey and Dawson volunteer to help at a charity run at Chicago Medical when a massive explosion sends Chicago into chaos. With one of their own missing in the blast, the firehouse is tested like never before.

The crossover continues on Chicago P.D. S01E12 8:30 PM (II)

With everyone’s support, Dawson makes final preparations to retake the fireman’s exam, but a call to the field may throw a major wrench into her plans. Elsewhere, Lt. Casey has an important matter to discuss with Antonio. Meanwhile, Lt. Severide and the firehouse welcome Rick Newhouse , the latest addition to the squad, Shay gets an uninvited surprise guest and Chief Boden makes a bold move.

A fire at a boarding school leaves Lt. Severide shaken and wondering if he could have done more. Meanwhile, with the firehouse in full support of Dawson as she retakes the fireman’s exam, Lt. Casey attempts some political maneuverings on her behalf. Elsewhere, Mills looks for answers about his father’s mysterious past and Chief Boden’s grand plans take a detour.