Al Policlinico arriva una nuova studentessa al terzo anno, Lucy Knight. Già al suo primo giorno si dimostra competente e preparata. Sarà affidata al Dottor Carter. Doug deve essere supervisionato da Kerry come conseguenza della sua decisione di avere sottoposto un bambino di sette mesi a disintossicazione rapida senza il consenso della madre. La Dottoressa Dell'Amico ha lasciato il pronto soccorso per trasferirsi a Philadelphia. Al Dottor Greene viene proposto di diventare coordinatore dei paramedici.

Dr. Corday's father visits from overseas in an attempt to convince her to join his medical practice. Weaver suggests that Elizabeth look into alternative methods to stay in America, like starting over as an intern. Weaver also doesn't let an opportunity pass to remind Doug of the way he bypassed her authority in the McLean case. Lucy continues learning, earning more of Carter's respect than she deserves. Peter takes Reese in for another hearing test. Mark has several discussions with paramedics about the state of the EMT program. Carol hires a nurse practitioner to help out in the clinic. Carter is having trouble being an RA in the dorms.

Mark goes to a trauma scene with the EMTs, where he treats a gunshot victim who has a bomb strapped to himself. Later, Mark’s daughter persuades him to treat a horse with colic, and Jerry gets the bad end of the enema. Carter intubates an elderly woman who is DNR. When her HMO declines to admit her, Carter either has to find a relative quickly or let her die. Kerry finds herself more and more frustrated when Anspaugh suggests that they're not considering her for ER Chief, and she discovers she’s the last to hear that Doug was made a pediatric attending. Corday serves her last day as a surgical fellow. Benton meets with Carla to discuss getting Reese hearing aids. Jeanie returns from vacation. Carter goes out with Roxanne, the insurance saleswoman he treated.

Dr. Corday begins her first day as an intern, first by being assigned to Dale Edson, then being treated as Romano's lapdog. Kerry is interviewed for ER chief. Doug and Carol ponder parenthood when Carol realizes she may be pregnant. Carol and Lynette try to keep a wounded gang-banger from leaving and seeking retaliation. Lucy faces the wrath of Carter when he discovers that she doesn't know how to start an IV. Jeanie asks Doug if she can be a full-time PA for the pediatric ER.

Halloween night finds the ER awash with allergic or otherwise incapacitated children. Kerry tolerates a visiting candidate for chief while she waits for the official vote. Romano operates on an 11-year-old girl and finds she's genetically male. Carter leaves Lucy in charge of a dorm party he's supposed to be overseeing, with unfortunate results. Mark learns that Jenn's moving to St. Louis--with Rachel. Mark and Carol treat a pregnant schizophrenic.

After Mark saves a 16-year-old assault victim in a daring rescue, he tries to convince the boy to leave the streets for a shelter. Carter loses his beard when two carpet installers come in covered with glue. Peter consults a deaf physician regarding Reese's hearing condition. Corday is reassigned as Benton's intern. Kerry hears more discouraging news regarding her bid for ER chief. Carter loses his RA job, forcing him to go apartment hunting. He finds one--in Weaver's basement.

Kerry e Carter diventano coinquilini. Elizabeth, dopo un turno di 36 ore, somministra una dose di letale di magnesio ad un paziente, provocando problemi a Benton, che in quel momento avrebbe dovuto supervisionarla in quanto sua tirocinante. Carter da la valutazione di Lucy da completare alla studentessa stessa, costringendo Greene a rimproverare entrambi. Jeanie e Doug trattano il figlio di una donna la quale sembra dipendere dalla figlia di sei anni. La gestione dell'ospedale viene affidata ad Amanda Lee.

Al pronto soccorso del Country General Hospital arriva una bambina, Corinna, insieme al padre vittime di un incidente stradale. La bambina presenta una lesione alla milza, ha bisogno di una trasfusione di sangue e di un intervento chirurgico. I medici scoprono che il gruppo sanguigno di Corinna è un gruppo raro e in ospedale non è disponibile sangue di quel gruppo specifico, l'unico che potrebbe donarlo è il padre. Il padre, intanto, approfittando di una distrazione di Lucy, che si apprestava a medicarlo, fugge dal pronto soccorso. La studentessa di Carter scopre che il padre di Corinna aveva fornito un nome falso, in realtà egli è il Sig. Nelson, è un allibratore e alcune settimane prima aveva sottratto Corinna alla custodia della madre. Tutti i medici del pronto soccorso si impegnano al fine di trovare sangue per Corinna.

Carter, rinunciando ad una gita in barca con l'amata Roxane, si mette sulle tracce del Sig. Nelson e nei pressi di un Hotel incontra la sua studentessa che aveva avuto la stessa idea. I due continuano insieme la ricerca e colgono l'occasione per appianare le proprie divergenze e dichiararsi stima reciproca. Al pronto soccorso, intanto, Kerry Weaver è riuscita a trovare due sacche congelate del sangue di Corinna, Benton si prepara ad eseguire l'intervento, però, nello scongelare il sangue i medici scoprono che le sacche presentavano dei fori e il sangue potrebbe essere stato esposto a batteri. Il Dottor Benton e il Dottor Anspaugh decidono di adottare una misura estrema; operare senza sangue. Durante l'intervento Corinna va in tachicardia ventricolare, i chirurghi riescono a riprenderla ma senza trasfusione di sangue la bambina morirà.

Lucy e Carter intanto riescono a scoprire l'indirizzo del Sig. Nelson e giunti a casa di quest'ultimo ascoltando la segreteria telefononica riescono a rintracciarlo. I tre arrivano in ospedale ma qui scoprono che la trasfusione forse non basterà a salvare la piccola Corinna che è entrata in coma.

Lucy e Carter si ritrovano a parlare della vicenda, Lucy sconsolata prende atto del fatto che non sono riusciti a salvare la bambina, Carter le fa notare che sono riusciti soltanto ad aumentare le speranze; questo però non è abbastanza per Lucy che non si accontenta. Carter, allora, spiega alla sua tirocinante che quando un medico fa tutto il possibile per salvare un paziente ma non ci riesce deve accontentarsi di averci almeno provato e le fa osservare come lei ci abbia stra-provato.

Carter plays tour guide for Ruth Johnson, who was born in the hospital 100 years ago to the day, and her large family. Carol treats a boy who was hit by a car and tells a story of being chased, his friend being shot in the process. Peter observes Kotlowitz install a cochlear implant and decides to wait before scheduling an operation for Reese. Mark dines with Dr. Lee, new ER chief. Dr. Corday proposes radical changes in scheduling at an M&M conference, and later decides to break off her relationship with Benton.

Benton's attempts to get away to Carla and Reese on Christmas Eve are continually thwarted by Romano, culminating in Benton forcing the drunken Romano away from a patient. Carter believes he's found a Christmas miracle when a teenage girl with a rare blood type needs an organ donation at the same time a brain-dead patient with the same blood type is in the hospital. After witnessing Dr. Lee rifling through Greene's locker, Jerry becomes convinced that she's stalking Mark.

Amanda Lee's obsession with Dr. Greene comes to a head when Mark inadvertantly digs up old med school records damaging to her career. Carter tries to save Lucy from Edson's advances. Peter treats Dr. Parks' grandchild, who interprets for her deaf mother and grandmother. Police officer Reggie Moore asks Jeanie out. Kerry receives a call from someone claiming to be her mother. Doug receives a job offer from Portland.

Doug jeopardizes future federal grants for the entire ER when he breaks a double blind study by giving a sample drug to an ailing patient. Doyle lodges a sexual harassment complaint against Romano, hoping Dr. Corday will lend support. Lucy begins her surgery rotation under Benton's tutelage. The two of them treat a man claiming to be 140-years-old. Mark declines to proceed in the NASA program. Carol questions Lynette's intentions when she hosts a women's health clinic for African American women only. Mark goes to bat for Pickman when she inadvertently leaves a severely injured man at an accident scene.

Ricky Abbott returns to the ER. Doug forges papers to allow Joi to treat Ricky at home. Corday decides to back out of the Romano sexual harassment investigation after he threatens to expose her relationship with Benton. Romano is later named Acting Chief of the ER. Dr. Greene treats a Nigerian janitor for back pain and impotency. Carol and the nurses watch a bunch of dogs when their owner is hospitalized. Carter diagnoses a med student with Hodgkin's disease. Kerry initiates a search for her biological parents.

Doug faces possible criminal charges after Ricky Abbott dies when Ross bypasses system lockouts to enable Joi to give Ricky a lethal dosage of dilaudin. Doug is delegated to desk duty, Carol's clinic is shut down for acquiring the P.C.A. machine for Ricky, and Greene and Weaver face future disciplinary action for not reporting Doug's tampering with the double blind study. Carter and Lucy discover a mutual attraction. Benton studies with a sign language instructor.

Greene assists paramedics in treating injured children at a school bus accident. En route, Doug and Jeanie survive their own accident. Kerry stops Doug from treating Jeanie...or any other patient. Doug decides to resign and leave Chicago for the Northwest and asks Carol to come with him. She decides against it, but he leaves anyway. Carol steps down from running the clinic so that Anspaugh will keep it open. Jeanie discovers she may have contracted hepatitis. Hospital janitor Mobalage's wife is stabbed.

Peter accepts Romano's suggestion and takes a two-week job in Minnesota to earn some extra money. Unfortunately, before he gets a chance to leave, he's transferred to backwoods Mississippi, where the hospital is only a two-room building. Peter battles local racism, delivers a difficult infant while battling the grandfather's concerns that the child might be black, and uses unorthodox methods to save two shrimp boat workers. Meanwhile, back in Chicago, Jeanie's condition worsens.

During a paramedic ride-along, Carter is forced to drive the ambulance while fleeing a riot scene and inadvertently runs over a teenage boy. Later, a paramedic is shot by an angry mob looking for the driver of the ambulance. Carol is despondent following Doug's departure. She later discloses that she's pregnant. Kerry is intrigued by an injured pro wrestler and his relationship with his father. Lucy tangles with an Asian family that requests their matriarch not be told of a cancerous tumor. Jeanie turns down dates with both Dr. Baker and Reggie, telling each she's seeing someone else.

Greene tries to help Mobalage when he's about to be deported. Kerry tries to save a woman she believes is her birth mother. Hathaway decides to have Doug's child. Benton and Corday clash over an ER fellowship. Carter is in charge for the day, part of a requirement for applying for chief resident.

Romano forces Benton to choose between the trauma and cardiothoracic fellowships. Carol worries that she may have lost her child. Corday and Greene bond on the way to a medical conference. Carter mentors an aspiring teenager. Lucy, on a psychiatry rotation, treats an overmedicated foster child. Jeanie finds her faith while treating a reverend.

The hospital suffers through a series of power outages. Carol's decision to send Doug a fax about her pregnancy is thwarted by the power outages. The staff is on alert after a raped and beaten patient is found in a hallway. Romano begs Corday to stay in trauma. Carter and Roxanne break up. Carter and Lucy treat a pheromone saleswoman.

The ER docs tend to three teenagers who were in an accident on the way to their senior prom. Greene and Carter treat the most severely injured, a boy suffering from third degree burns over 80% of his body. Benton receives the ER trauma fellowship. Carol finally tells Doug about her pregnancy; Kerry also figures it out. Mark and Elizabeth draw closer. Lucy tells Carter about her Ritalin addiction. "FBI agents" bring in a shot stripper.

Carol's pregnancy becomes public knowledge as she learns that she's having twins. Lucy has problems trying to go off Ritalin. Peter learns Carla plans to move to Germany. Kerry finds an abandoned youngster and brings him to the ER. Mark and Elizabeth discuss their relationship. Jeanie and Reggie draw closer again.