Nurse Lockwood gets arrested when she takes a stand. Meanwhile, Dr. Halstead deals with a pending lawsuit against him; a baby's injuries come into question; Dr. Charles faces personal issues; and suspicions rise about a patient who was hit by a car.

April and Dr. Halstead clash over how to treat an alcoholic homeless man with a broken leg. Also, Dr. Manning continues to grieve over her husband's death; two elderly women with the same symptoms share a surprise link; Halstead mulls over a job offer in California.

Dr. Manning and Jeff Clarke are forced to figure out a mystery illness when an Indonesian man who doesn't speak English arrives at the hospital in dire straights. Maggie takes Dr. Halstead to her family reunion. Dr. Rhodes takes on a complicated heart surgery without consulting Dr. Latham. Dr. Reese and Dr. Charles encounter a woman experiencing an unusual pregnancy.

Sharon Goodwin's childhood sweetheart arrives at the hospital, but finds himself in dire straits. To help get his financial footing, Dr. Halstead gets lured into a concierge doctor app idea. Meanwhile, a young woman with a heart infection is treated by Dr. Rhodes against Dr. Charles' advice and Reese's former patient, a sex trafficking victim, reaches out to her for help.

Dr. Manning and Dr. Charles treat a teenage girl with a rapidly changing set of symptoms that has everyone perplexed. Dr. Choi and medical student Jeff Clark encounter a 19 year-old tough guy who is brought into the hospital in severe distress. Once they establish the cause of the pain, the situation quickly turns dangerous and a resolved Dr. Reese does her best to help. Dr. Halstead must deal with a difficult case that is further complicated by Dr. Stohl, who has a camera crew following him around to shoot a promotional video spotlighting the hospital.

A hacker demanding a ransom payment shuts down the hospital computer system, forcing the doctors to diagnose patients without the aid of technology. A stressed Goodwin struggles to keep the hospital afloat when an unexpected visit from her ex-husband Bert and his new girlfriend make matters worse. Making use of his former navy experience, Dr. Choi and Noah have to locate a bullet inside a patient with a gunshot wound. Meanwhile, Sarah feels Dr. Charles may be trying to push her out and Robin's unusual behavior worries Dr. Rhodes.

Dr. Rhodes challenges Dr. Charles and other hospital staff over the proper treatment for Robin. Dr. Manning seeks help from Det. Halstead when a sensitive case involving a young girl turns into a crime. Dr. Choi and April work together on a conflicting case. Meanwhile, Goodwin helps a friend in distress and, after eagerly awaiting, the doctors are surprised to learn who the new med resident is.

The doctors of Chicago Med take their opinions to the extreme as they try to bring justice to the perpetrator in the shooting of Dr. Charles. Dr. Halstead and Dr. Manning work on a heart-wrenching case that forces them to examine their own matters of the heart. Though Robin’s brain tumor was removed and she is discharged from the rehabilitation center, Dr. Rhodes remains on edge that her problems are not quite resolved. Meanwhile, Rhodes gets blindsided by his colleague Dr. Bekkar, Maggie sticks up for a patient and Dr. Choi and April try to navigate their new working relationship.

Dr. Manning rushes to save a young boy with a life-threatening case of the flu; April suspects Dr. Choi's sister stole opioid pain killers; Dr. Rhodes and Dr. Bekker disagree over the best treatment for a cardiac patient who is 21 weeks pregnant.

When things become complicated, Will is forced to lie to Natalie. Ethan and April find out some compromising information about Emily's boyfriend and Ava is unsure of what to do with a patient who is refusing treatment.

Will and Natalie prepare for their big day, but an unsuspecting Will soon finds himself sidetracked. Dr. Charles disagrees with Goodwin on how to best handle a patient's treatment while Dr. Choi and April are on their own when a pregnant woman delivers. Dr. Rhodes finds himself operating on a patient that is of great importance to Det. Halstead.

Halstead hides the theft of his gun from a suspicious Manning. Tensions are still high between Connor and Bekker, who take a risk operating on an HIV-positive patient. Hank breaks down when he sees a patient from his past.

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.

Dr. Choi and Dr. Charles have difficult decisions to make as a dying man tries to preserve his life with a controversial scientific method. Dr. Marcel and April clash over how to handle a mysterious patient. Will questions Natalie’s capabilities.

Dr. Halstead's world is thrown into turmoil when a former patient resurfaces. April has a secret she considers confessing to Ethan. Dr. Charles tries to maintain his focus during a difficult time.

Goodwin announces a new ED Chief and the choice doesn't make everyone happy. Dr. Manning takes a stand for her patient and finds herself dealing with the repercussions. Dr. Charles tends to family affairs.

As Maggie deals with her own trauma, she steps in to help a mother in need. Dean continues to stir the pot with more than one doctor. A patient comes to Med needing immediate treatment, but doesn't want it from them.

Third-year med students begin their rotation in the ED and Maggie keeps a careful eye on one of them. Natalie, whose mom's health takes another decline, tries to cover up how she broke the rules to treat her.

Crockett helps Dr. Blake replace a patient’s liver. Vanessa tries to prove herself. Will continues to pursue the truth about Cooper. Ethan gets closer to returning to life in the E.D.

Will and Stevie get stuck in the middle of a marital face-off. Dr. Blake's entire surgical team mysteriously collapses during a liver transplant. Charles encourages Ethan to reconcile with his father.

Scott suspects his patient may be a drug dealer. Halstead must decide how to spend his whistleblower settlement. Charles and Taylor help a patient who believes she's infested with parasites. Marcel and Blake are paired with an arrogant surgeon.

Halstead and Asher work to save a surrogate's baby. Charles cares for a patient on a hunger strike. Choi and Archer help a patient with ties to Choi's late father. Scott and Maggie are stumped by a drunk patient who claims to be sober.

Med runs out of scrubs, forcing the staff to improvise. The life of Archer’s son is in danger. Marcel and Charles help a kidney transplant patient experiencing psychosis. Asher and Halstead grow closer.

A brutal storm rocks Chicago. Halstead encourages Dr. Grace Song to go against her own findings for the benefit of their patient. Asher rushes to the hospital to help Archer's pregnant patient. Maggie's concern for Ben consumes her.

The fate of the hospital rests on the vote of an incapacitated board member. Archer helps a mother with a rare stem cell disease while Asher treats the woman's pregnant daughter. Charles encounters a schizophrenic patient with a hearing impairment.