Dr. Charles and Caroline set some major plans. Ava fights to keep her relationship with Connor. Agent Lee informs Will of news that may put his life in danger.

The hospital goes into lockdown mode when a man with a gun holds medical staff hostage. Goodwin is forced to make a tough decision. Dr. Rhodes begins to realize his time with his father is getting short.

Following the subway tunnel collapse, Ruzek and Kidd treat injured passengers and track down the missing offender. Archer and Frost perform a life-saving amputation. The crossover starts on Chicago Fire S13E11 In the Trenches (I). It continues on Chicago P.D. S12E11 In the Trenches (III).

The team fights to save the life of one of their own. Frost and Abrams butt heads with their patient. Asher helps a religious young woman with an ectopic pregnancy.

Dr. Charles and Dr. Manning disagree on how to handle a patient who they discover is poisoning herself. Dr. Rhodes throws some serious accusations at Dr. Bekker. Dr. Halstead has suspicions about Natalie’s new boyfriend and Dr. Choi tends to Bernie.

Ripley struggles to rescue a woman and her daughter trapped in an abandoned well. An old friend from Frost's TV days shadows Maggie. Asher discovers an extremely rare condition in her patient's ultrasound.

Charles and Archer treat a heart transplant patient who believes his new heart doesn't want to be in his body. Lenox takes a personal day. Asher discovers a mass on a pregnant woman's ovary.

Dr. Manning's actions with a recent patient lead to serious repercussions. April and Noah disagree over a patient who is injured after a beating. Dr. Charles is visited by a childhood friend with a surprising revelation. The crossover starts on Chicago Fire S08E04 Infection (I). It continues on Chicago PD S07E04 Infection, Part III (III).

Goodwin's troubles persist. Charles clashes with his former resident over a depressed patient. Lenox and Ripley treat a car accident victim who recently reunited with his college sweetheart.

Asher treats a woman whose undiagnosed condition threatens the lives of both her and her unborn child. Goodwin receives a chilling message while battling the hospital higher-ups.

Maggie and Frost fight to get a pair of lungs for a young cystic fibrosis patient. Asher learns whether she can become a surrogate. Ripley and Morris treat a tech billionaire's daughter as she battles leukemia.

Goodwin is tasked with enforcing difficult cuts to hospital personnel. Charles' daughter is hospitalized after a car accident. A transplant patient makes a life-changing decision.

Chicago Med braces for an influx of trauma patients when a pre-dawn pileup finds the hospital in full scramble mode. As a result of the storm and emergencies, supplies become limited and Goodwin, Dr. Manning and Dr. Halstead must deal with making an impossible decision. Meanwhile, Dr. Choi handles a severely burned patient who has one final request and Dr. Charles deals with an agitated patient.

A suicide shakes the staff. Dr. Choi and Dr. Halstead face off over how to treat a patient with stroke symptoms. Family turmoil unfolds when a boy is treated after falling in a river. The importance of learning from mistakes is emphasized to Dr. Reese.

A new hotshot doctor arrives at Chicago Med causing competition for Dr. Rhodes, Dr. Halstead and Dr. Manning work together to diagnose a Syrian refugee without a medical record. When Robin is admitted back into the hospital for more complications, Dr. Reese takes a different approach to her treatment. Distracted from work because of Robin's worsening case, Dr. Charles is challenged by Goodwin and Noah hosts a graduation party that brings everyone together.

After a major accident at O'Hare, the E.D. is concerned one of their own is in mortal danger. Will's proposal for a safe injection site goes to the board for consideration. Natalie and Goodwin become concerned for Gwen.

Ripley and Charles treat a high-risk prisoner who may have dementia. Archer and Sean clash when a resident from Margo's facility lands in the E.D. Marcel receives shocking news.

An army of surgeons prepares to separate conjoined twins. Asher reconnects with someone from her past. Archer treats a tyrannical boss with a heart problem.

Asher makes a tough call to save a life. Frost and Ripley treat a young boy with a snake bite. Archer gives Naomi a patient to handle on her own on her last day in the E.D.

The hospital faces a staffing crisis as the nurses stage a sick-out. Archer and Frost bet on who can discharge their patients first. Charles' distrust of a patient complicates his treatment.

Dr. Rhodes treats his mentor and Goodman faces personal issues in the Season 1 finale. Also: April deals with a disorderly patient; Dr. Manning's past catches up with her; and Sarah's graduation day arrives, but she remains conflicted about her future.

After a shooting occurs during a block party, the staff is overrun with victims; Dr. Choi devises a new mass casualty plan; Dr. Manning struggles to stay focused when she realizes her son and nanny might have been at the scene.

Connor, who is in hot water with the hospital's Oversight Committee, handles a gunshot victim with unexpected ties to Halstead. Maggie feels guilty about the return of a former patient. Charles has an awkward first date.

Natalie and Maggie witness a pickup truck plow through a street fair and must make tough decisions on the fly. At the hospital, doctors and nurses are on high alert with the influx of patients. Dr. Charles' ex-wife comes to town with news.

When a car unexpectedly smashes through the ambulance bay doors, Dr. Choi makes some difficult decisions in an effort to save a worker trapped beneath the wreckage and April, who's also in danger.