While conducting an autopsy on a Petty Officer who is believedto have died from natural causes, an armed man enters themorgue and holds Wade, Sebastian and Danny hostage.
When Clive identifies a John Doe in the morgue as one of hisformer criminal contacts from his days on the vice squad, Livis surprised that Clive is so quick to refuse her help insolving the murder. Liv and Ravi investigate on their own whichputs them in a precarious situation. Liv's problems continue tomount when Major begins searching for a roommate and shebelieves he's considering a cute co-ed.
The community turn out in force for the murder trial and Ianfeels wracked with guilt about Ramu's arrest and he gets readyto act as his alibi. Sooni takes advantage of the trial to gainsome much required legal experience.
Jessica’s superstitions get the best of her when she sells ahouse with the address 44 West 44th Street – the number 4being bad luck in Chinese culture. At the urging of the newschool counselor (guest star Judah Friedlander as Ray), Eddiedecides to run for school president, but Jessica’s bad luckgets the best of him too when a white lie spirals out ofcontrol.
With only a few days before Joe Carroll's execution, Ryan andMike shift their focus to a new threat. Meanwhile, after beingapproved to start work again, Max rejoins the task force andcomes dangerously close to a deadly menace.
Peter delves further into Emma's mysterious past, whichultimately leads him to uncover an ancient symbol that has beenhidden for centuries. At the compound in New Mexico, someonefrom Debbie's past attempts to rescue her. Lynn's life is putin jeopardy.
Having been thrust into a dark place from where it looks likethere is no coming back, Banks' mission to solve Annie'smurder is made all the harder by the fact he has been taken offthe case and sent on gardening leave – but that won't stophim. While his old team struggle, Banks operates for the firsttime on the other side of the law, using his years ofexperience, wits and wisdom to secure the all-importantbreak-through. It finally looks like Banks has done theimpossible and is on the verge of bringing crime boss SteveRichards to justice when the case takes an unexpected twist,sending Banks and the team back to square one. Will Banks beable to come out on top after an explosive confrontation withRichards – he needs to try and begin to rebuild his shatteredworld.
Helen is determined to try and win back Banks's approval asthey attempt to discover the true identity of student Josh'smurderer and stop his father from seeking a revenge of his own.
It's all hands on deck when Firehouse 51 races to the scene ofa deadly chemical leak inside an industrial building. Withsquad and truck tested like never before, scores of workersare rescued but many are experiencing respiratory distress.This prompts truck 81, squad 3 and ambulance 61 to spring intoaction to transport the victims to nearby Chicago Med. Thesituation takes a turn from bad to worse in the midst of thechaos when a "patient" planted inside the hospital goes on asuicide mission armed with a grenade and claiming to be thecarrier of a deadly airborne disease. Trying to stop the madmanfrom engaging the explosive device, a member of the firehouseteam is severely wounded in the blast and left to facelife-threatening injuries. With no other choice, Chicago Medis forced into lockdown until doctors and the Hazmat team candetermine the severity of the airborne virus.
A self-proclaimed "nightlife expert" afflicted by mounting debtand a ballooning ego butts heads with Jon Taffer as he battlesto show him the error of his ways.