Dr. Carter begins his surgical internship, but his first shift as a doctor is not what he expected. When 4th of July casualties inundate the ER, Carter is reassigned back downstairs -- and forced to make life or death decisions on his own. Jeanie and Benton receive the results of their HIV tests. Ross fails to convince Dr. Greene of the joys of being single. Hathaway's financial situation forces her to return to work.

Jeanie struggles with her decision to keep her HIV-positive status a secret and also starts receiving Al's medical bills. Lewis and Greene bond over their pathetic social lives and recent dating disasters. Hathaway considers selling her money pit of a house, until her mother intervenes. Carter treats his elderly neighbor. When a nearby hospital is shutdown, its staff is merged with County General's; Dr. Donald Anspaugh is brought in as the new Chief of Staff.

With the merging of now-defunct Southside and County General, the ER gains a new intern, Maggie Doyle and must contend with their new Chief of Staff, Anspaugh. The patient load also increases. Weaver learns about Jeanie's HIV status; Benton transfers out of Anspaugh's cardiothoracic elective to work with a pediatric surgeon, Dr. Abby Keaton. Carter's neighbor, ignores Carter's advice and smokes while using her oxygen tank -- consequently blowing up their apartment building.

Benton is busted by Dr. Keaton for his lack of compassion for the pediatric patients and families. Carter, on the other hand, is praised for understanding the emotional side of medicine. Carter also moves in with Gant since he is temporarily homeless after an apartment fire destroyed his place. When a seizing woman is brought into the ER, Ross recognizes her as his one-night-stand from the night before. However, he can't even remember her name. Greene turns down Lewis's offer to vacation in Hawaii, but agrees to apartment-sit for her while she's away.

The Halloween shift starts off with a bang when an injured Frankenstein arrives with a gunshot wound to the chest. Gant and Carter compare evaluations and Gant discovers that Benton is being tougher on him so that no one thinks his race gains him preferential treatment. Jeanie clashes with the new intern, Doyle over a DNR patient. Hathaway and Ross take the maiden shift in Anspaugh's baby - the mobile health van. Lewis returns from vacation -- but doesn't admit to Greene that she didn't go to Hawaii due to her fear of flying.

In response to a remote, near-fatal car accident, doctors Greene and Lewis ride in a rescue helicopter to help the victims. Lewis momentarily gets over her fear of flying and arrives on scene to help a family of four involved in the crash. When the parents, their seven-year-old son and infant daughter are airlifted back to the ER, it's up to Benton and the others to save them.

While obsessing over a critically ill baby in his care, Dr. Benton uses heroic measures to sustain the life of a gang banger already declared brain dead by Dr. Ross. Ross is again second-guessed when Dr. Greene steps in to diffuse Ross's argument with the father of a 6-year-old boy with an infected wound. Dr. Carter's suspicion that a surgical patient has psychological problems leads to a confrontation with Dr. Dale Edson. Nurse Hathaway continues to clash with an inexperienced nurse, who makes another serious mistake. Dr. Greene treats a slightly injured social anthropologist who gives him new insight into human courtship behavior.

Dr. Lewis and Dr. Greene are faced with a personal decision that will affect both their futures. Dr. Keaton tries to teach Dr. Benton a new approach to surgery. Nurse Hathaway fights with the nursing administrator over her staff being pulled out to float in other departments. Jeanie is surprised at Al's sudden maturity. When a drunk woman comes into the ER in labor, Dr. Doyle reports her to the police. On Healthmobile duty, Dr. Ross bends the rules to help a teenage girl, Charlie, who brings in a friend's baby for vaccinations. Nurse Wright and Officer Grabarsky's wedding plans take an unexpected turn.

With the ER understaffed since Lewis's departure, Greene steps up to take a more active and strict interest in running things. After treating Al Boulet, Greene becomes suspicious of Jeanie and investigates her health status. Carter and Keaton continue their intimate relationship. Hathaway continues her pre-med studies but oversteps her boundaries with Weaver.

While Dr. Greene and Dr. Weaver work out their differences regarding a policy for HIV-positive workers, Jeanie decides to put a stop to the rumors that a staff member has AIDS. Dr. Carter asks Dr. Gant to spend the holidays with his family, then backs out to accept an invitation from Dr. Keaton. Charlie, brings a seriously ill baby in to see Dr. Ross. Dr. Doyle treats a battered woman and helps her escape from an abusive husband. A severely burned homeless man makes Greene promise to look after his dog, Nick. Dr. Benton has a disappointing conversation with Keaton. Ross drops in on Nurse Hathaway's traditional Ukrainian Christmas to ask a favor.

Dr. Weaver talks Jeanie into assisting in a study on the effect of exercise on night-shift workers. Dr. Greene, battling with the hospital attorney who refuses to let him treat an incoherent patient, finds an unexpected friend in Nurse Marquez. Nurse Hathaway's solution to the hospital's budget crises upsets the nursing staff. When Charlie, reappears and asks Dr. Ross for another favor, his refusal to help unwittingly puts her in a dangerous situation. Dr. Carter avoids listening to Dr. Gant's personal problems, and sneaks off to a rendezvous with Dr. Keaton. Frustrated in his attempt to secure another pediatric surgery rotation, Dr. Benton takes out his anger on Dr. Gant in front of the hospital staff. Later, Benton, Carter and Doyle frantically work to save a man who threw himself in front of the train -- and soon realize it's Dr. Gant.

Guilty over Gant's death, Carter blames himself for not being a better friend. Benton remains unwilling to talk about the matter, further irritating Carter.Charlie asks Ross to be her guardian -- but Ross refuses. Meanwhile, the nurses stage a sick out to protest cuts in overtime pay, leaving Hathaway to pick up the slack. The result is the death of a homeless man that Hathaway administered the wrong blood to.

Carter confronts Benton about his inability to deal with Gant's death. Benton must also deal with the fact that his former girlfriend, Carla, is pregnant as a result of their recent night together. Greene and Marquez break off their romance; Greene is encouraged by Anspaugh to pursue a teaching position. Labor relations uses Hathaway's screw up to thwart negotiations with the other nurses, until Hathaway takes total responsibility for the incident and gets suspended. Ross treats a boy who is convinced he is Superman.

Newly single Dr. Greene cancels a date so he can instead juggle two other women on the same night. However, all three discover the truth and one, Dr. Pomerantz is particularly peeved. Doyle and Carter learn to cooperate when Doyle takes Carter to a rifle range and teaches him to shoot. Carter performs an appendectomy on Benton and Nurse Haleh Adams takes over for suspended Hathaway.

Nurse Hathaway is among those shopping at a family-owned convenience store when a robbery attempt goes awry. The store owner injures one of the robbers, James, and is badly wounded himself when the second robber, Duncan, panics and takes everyone hostage. While police cars gather outside the store, Hathaway must use her medical skills and the crude implements available in the store to keep the wounded alive and to maintain calm among the hostages and the gunmen. She finds unlikely support from her 10-year-old neighbor, Robert. Meanwhile, Dr. Ross and the hospital staff anxiously await word as the crisis unfolds.

Dr. Benton's attempt to placate Carla is met with contempt, and he returns to the hospital for the first time since his appendectomy. Dr. Carter is working extra-long hours to cover shifts left vacant by Dr. Gant's death, but he manages to catch another doctor's critical error. When Dr. Greene learns that a 37-year-old Down's Syndrome patient with an enlarged heart has been denied a heart transplant, he takes the matter up with Dr. Pomerantz. Complying with the demands of an 18-year-old cystic fibrosis patient, Dr. Ross must remove the respirator which keeps the boy alive. Following her suspension, Nurse Hathaway is reinstated at the hospital and decides to take the medical admissions test. Jeanie and Dr. Fischer continue their tentative relationship with a second date.

When two teenagers -- one white and one black -- are brought in with gunshot wounds, Dr. Greene must deal with his own racial attitudes, angry family members and a retaliation shooting. Dr. Carter struggles to diagnose a patient previously written off as a crack addict. Nurse Hathaway treats a young victim of date rape. Dr. Benton is forced to get involved when Carla comes into the ER with minor injuries from a car accident, and Jeanie discovers other complications. Dr. Weaver tries to convince an injured paraplegic man to enter a detox program. Dr. Hicks makes an unexpected offer to Benton.

Greene struggles to juggle the demands of the ER and his increasingly problematic daughter, Rachel. Nonetheless, he agrees to write an article for a medical journal in order to better his chances for a teaching position at the hospital. When Anspaugh refuses to perform a complicated surgery on a lost cause, Carter goes behind his back and gets Hicks to do it. While the patient survives, Carter is placed on probation. Benton tells Carla he wants to accept financial responsibility for her and his baby. Hathaway awaits the results of the MCAT.

Hathaway passes her MCAT with flying colors and Weaver begins treating her like a med student. However, Hathaway decides that she loves nursing too much for a career change. Benton discovers that Carla has diabetes, which gives him concern for his unborn child. Carter fails to report Edson's misdiagnosis, fearing that Anspaugh wouldn't believe him anyway. A genetically engineered mouse escapes the lab and runs loose through the ER.

Benton acts as Carla's birthing coach, but she wants someone less critical and more reliable. Jeanie tries to get her HIV-positive, ex-husband into her current boyfriend's AIDS study. Greene is threatened by the brother of a gunshot victim who was caught in the crossfire of a drug dispute. The victim, a black man, died while the white drug dealer survived. Later, in the hospital bathroom, Dr. Greene is viciously attacked by an unknown assailant.

Carla goes into labor eight weeks early, causing a frantic Benton to overstep his bounds. Benton and Carla grow further apart as their baby's life hangs in the balance. Carter contemplates whether or not he's cut out to be a surgeon, while Jeanie rekindles her relationship with Al. Ross helps the nurses surprise Carol with a birthday party. Greene, battered physically and psychologically, returns to work amid heightened security.

Carter decides he wants to give up his surgical residency to pursue emergency medicine, even if it means working for free. Surgery is performed on Benton's premature baby, but he fears permanent brain damage. Greene destroys the doctors' lounge prompting Ross and others to confront him about his tenous mental state. Charlie, the 14-year-old that Ross met through the Healthmobile, arrives in the ER after a drug overdose. Later, Ross and Hathaway share a kiss.