Watters' old romantic rival checks into the hospital in need of a heart transplant. When a heart finally arrives, Austin performs the transplant against her will, believing that the wealthy patient bribed the donor family. Aaron and McNeil work together to help a man with a rare disease that is causing his muscles to contract. Wilkes is affected when a gang member violently shoots up the ER. Billy officially asks Diane to marry him. It's mentioned that Nyland is gone, it doesn't say how or why.
Billy removes the kidney of a 9-year-old girl with an extensive medical history, and discovers signs that she's being abused. He suspects the girl's mother may be intentionally harming her daughter to grab attention. Aaron grapples with himself when he loses a patient while performing a simple procedure. Kate can't break away from the hospital to attend her daughter's school carnival. Jack gets caught in a sting at Bart's bar, prompting Phillip to insist that Jack enroll in Gamblers Anonymous.
Aaron announces he's leaving Chicago Hope for a teaching position at Harvard. Shortly thereafter he begins to suffer from a brain aneurysm. The aneurysm sends him into a trance state where he hallucinates several strange fantastical experiences, including Chicago Hope doctors in song and dance sketches and Jeffrey Geiger's advice on life.
The staff worries about Aaron when he has a series of seizures, threatening his chances to survive another operation. Jack refuses to allow a drug addict to go through a super fast detox program, using the knowledge he's gleaned from his attempts to beat gambling. A child molester asks Billy to castrate him.
Austin struggles when a girl with Down's Syndrome offers to donate a lung to her needy brother. Dennis surprises a benefactor with the news that one of his relatives was black. Dr. Grad discovers that she's pregnant, just as Billy announces plans to take a four-month sabbatical.
Billy and Diane are married as Billy rushes off to South America. Diane is horrified by a teenage girl who dumped her newborn child into the trash. Dr. Austin treats a high school basketball player with a bad heart who's reluctant to quit the game. While trying to counsel a male rape victim, Aaron becomes intrigued with the mechanics of the brain. Kate connects with electrician Danny Blaines, but remains reluctant to be seen with him in public.
Jack and Kate operate at 20,000 feet on a pregnant woman while the two are flying to a medical conference in London. Aaron begins his psychiatric residency, getting off to a bad start with his teacher and falling prey to his patients' manipulative disorders.
A 'girls only' weekend getaway at McNeil's cabin goes horribly wrong for Kate, Lisa and Diane, when Grad is assaulted by a native backwoodsman. The three doctors deal with the attack differently. Austin, still affected by an attack in her college days, responds with anger. Lisa remains cool and rational while Diane is paralyzed with fear.
Dr. Shutt counsels the family of a teenage suicide. McNeil and Hancock try to determine whether a young patient is the victim of parental abuse. Wilkes refuses to treat his absentee father after he's admitted to the hospital. Phillip, stinging from repeated rejections from his son, urges father and son to reconcile.
Phillip is disturbed to learn that his accountant has stolen every cent he owns. Watters' pride doesn't let him accept offers to help from both Jack and Aaron. Shutt and Dr. Catera clash over a patient's suggested treatment. Keith is arrested for drunk driving and is sentenced to community service work at Hancock's clinic. Diane's loneliness sinks her Holiday spirits. Jack plays Santa for sick children.
Phillip reconnects with an old flame when her son is hospitalized. Jack decides to pursue a relationship with Lisa, dumping Karen Wilder. Grad is busy with a patient who insists she's pregnant despite evidence to the contrary.
Chicago Hope's doctors struggle with adversity when the power goes out on a blustery, winter night. Keith endures a drunken Irish engineer to try to get a backup generator on-line. Dr. McNeil tries to explain life and death to Sara Wilmette and Cacaci's son when they're trapped in an elevator together. Aaron strives to help a teenage girl found bleeding from her hands in a church. Billy contends with a pregnant (and hormonal) Diane. Kate doubts herself when a very expensive computer program disagrees with her diagnosis.
Phillip, temporarily hobbled with a leg injury, spies a murder through his telescope and tries vainly to convince police he really witnessed a killing. Danny Blaines gives Kate a bird which gets loose and flies throughout the hospital. Diane locates her birth mother and visits her and her extremely strange house.
Diane faces her impending motherhood full of doubts, inspired by an HIV-positive patient who wants to have a child, and the discovery of a mass in her breast. Wilkes and Hancock are swamped with a pregnant teenager who's handcuffed to her abrasive mother. Dr. Catera attempts to remove half of a five-year-old's brain to stop her seizures.
Phillip decides to take a stab at open-mike comedy, to his colleagues horror. Lisa finds herself attracted to Jack's incarcerated brother. Austin and Sara dine with Danny Blaines, leading to a violent confrontation. Billy, worried that his impending fatherhood has made him weak, gets into a midnight bar fight.
Billy treats a family with damaged livers via poisonous mushrooms. The father, the only unaffected family member, must choose which of his two sons will receive part of his liver. Aaron sees a troubled patient who, through hypnotherapy, claims she was sexually abused by her father. Phillip forces Kate to attend a touchy-feely medical conference with Cacaci. Billy gets he and Diane thrown out of Lamaze class. Diane debates whether to tell Billy what really happened at Jack's cabin.
Phillip, Jack, Aaron, and Keith travel to Las Vegas for a medical conference. Jack, confident he's beaten his gambling addiction, runs into an old friend, the father of a boxer. The boxer dies, sending Jack spiraling downward, culminating in another descent into gambling.
Dr. Wilkes treats identical teenagers with the same rare heart ailment, losing one in the process. Kate treats a 10-year-old who nearly died after sniffing glue, and learns her daughter does the same. Aaron interviews a man for inclusion in a study by Dr. Frank. Diane debates taking maternity leave. McNeil isn't sure whether a man has sentiment or politics at heart when he insists life-saving surgery be taken on his sister, over her same-gender partner's wishes.
Diane, several weeks overdue, finally goes into labor. Wilkes tries to keep an abusive man away from his family by admitting him for back pain and doping him up. Jack and Lisa take a ballroom dance class.
Aaron supervises a famous painter when she's admitted with a brain tumor. Dennis treats a young boy who believes himself to be a girl. Dr. Wilder clashes with Kate over the proper treatment for an unborn child.
Aaron and Samara vacation in LA, where Aaron learns a valuable lesson about savoring life. Keith clashes with Dennis when a wealthy woman tries to improve urban life by paying for the sterilization of drug addicts. Billy endures a visit from his flighty mother. Phillip tries to produce an audio tape on surgery.
Raymond Wilkes is traumatized when he's caught in the middle of gunfire at his school's playground. Keith questions his parental instincts when his first thought is to treat the wounded rather than protect his son. With no one else around, Aaron is forced to cut into a patient to save his life, and does it successfully. Kate and Lisa seek counseling for the cabin incident. Jack makes a commitment to Lisa. Phillip reconnects with Stephanie.