Mark and Kerry have to create a policy regarding HIV-positive employees, which leads to gossip amongst the nurses.

Benton goes into Carla's private hospital files when he fears that something may be wrong with their baby; Jeanie treats a suicidal woman who reveals a surprising secret; and Greene learns that Rachel has been lying about her health.

His ex-wife Jennifer tells Mark he can't see Rachel until he's got his act together. Reece gets to go home. Al has lost his job.

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.

Mark Green is in New York on New Years Eve for cancer surgery. Meanwhile a father and son are involved in a car crash.

Greene's daughter comes to live with him and Corday. Carter and Abby become more intimate. Chen must prove her skills while saving a baby. Weaver terminates Malucci after witnessing him having sex in an ambulance.

As Dr. Greene's brain tumor begins affecting his coordination, he becomes concerned that his fate will be similar to the terminally ill patients he treats.

Dr. Greene's final days are spent in Hawaii with Rachel, teaching her to drive and surf. When he suffers a seizure, Elizabeth is called. Mark refuses to go home. He manages to make amends with his daughter before his eventual death.