The latest threat intensifies, leaving Chester’s Mill residents at risk of being crushed to death; Melanie’s health declines as the egg’s fate remains uncertain.

Just as the walls start to close in on those trapped in Chester’s Mill, a possible exit from the dome is revealed.

As Barbie descends further into the mysterious tunnel in hope of finding Sam, he comes across a world filled with unanswered questions.

Barbie turns to his father for help contacting Julia but realizes that he may not be trustworthy; Big Jim declares himself sheriff of Chester’s Mill.

Barbie is apprehended by mysterious men and relentlessly interrogated about the Dome; Big Jim forms a deal that could permanently seal the fate of the Chester’s Mill residents.

Big Jim finally learns what happened to his wife, Pauline; Chester’s Mill faces a new threat — climate change.

Rebecca and Sam try to save Chester’s Mill residents as temperatures plunge; Barbie puts his life at risk to help Julia after a terrible accident.

Barbie’s life is in Big Jim’s hands; the dome becomes magnetized; Julia tries to save the life of a mysterious girl who may have clues about the origin of the…

Big Jim conducts a census to see how long the town can survive on dwindling resources; acid rain threatens everyone.

Mary works to solve the mystery of who tried to kill her witness, an art dealer. To complicate matters, both his mistress and his wife are in the program…and key…

It’s Susan’s last day. Carol stands up for her nurses when one of them is being rotated to another department.

While Mark is anxious about Susan’s return from her holiday, Doug and Carol ride along with the health mobile.

While on their helicopter flight rotation, Mark and Susan find an injured family of four who they bring to the ER.

Encouraged by Carol, Mark finally asks Susan out. Benton tries to save a boy, despite the fact Doug thinks he’s brain dead.

It’s the first day of Carter’s internship. He has a 36 hour shift and overnight he has to cover the ER, the ICU as well as the surgical patients.

While the whole staff is worried the ER might close, Jeanie has her own problems in dealing with being HIV-positive.

Donald Anspaugh has a new method to increase the staff’s efficiency, new intern Maggie Doyle joins the ER and Susan asks Mark to come along to Hawaii.

Doug’s one-night-stand has a seizure and he brings her to the ER.

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…

Just when the ER is understaffed and swamped, two children who were brought in turn out to have full blown smallpox. The entire ER must be locked down. The staff…

When Dr. Lewis gets a hysterical call from her niece, Susie, she hurries to New York to search for the child and her sister Chloe. The crossover continues on Third…

Dr. Carter reads a letter from terminally ill Dr. Green to the ER staff. Dr. Weaver lashes out at a mentally challenged patient. A terminal, homeless man continues asking for…

Drs. Corday and Greene are awkward when working together in the ER. Dr. Weaver treats victims of an intense fire that may take the life of a dear friend.

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.

After Dr. Corday moves out, Dr. Green fights loneliness and pain by immersing himself into his work. Dr. Chen discovers that a comatose teen is ready to give birth.

After some staff members are caught going through a dominatrix’s bag, Weaver makes them attend a sexual harassment seminar, where they learn about each other.

An injured and condemned murderer wants to die in the ER rather than await execution; Abby advises a neighbor to seek shelter from her abusive husband.

An accidental overdose brings Drs. Green and Corday’s baby into the ER.

Greene confronts Corday when she orders Rachel out of their home; Abby tries to protect a battered neighbor who refuses to press charges against her husband.

Peter Benton continues his court fight against Reese’s stepfather, Roger, who seems to have the upper hand. When a woman is accidentally shot during a gas station robbery, Dr. Corday…

Benton commits perjury on the witness stand in order to gain custody of Reese. When Romano refuses to give him a more even schedule, Peter resigns and seeks a job…

Abby helps a distraught boy whose mother died of a stroke; a man with schizophrenia, who once stabbed Carter and killed a doctor checks into the ER.

A new medical student, Michael Gallant, arrives in the ER. He’s supposed to be working under Dr. Carter’s supervision but his grandmother is unwell. Elizabeth Corday is convinced that other…

When a torrential rainstorm pounds Chicago, patients deluge the emergency room while Weaver speeds to an accident site. There, she finds a pregnant woman, Vicki lying injured inside a wrecked…

Lewis faces a hectic first day back at County General. Benton and Roger become frantic when they can’t locate Reese. Carter’s grandmother is brought to the emergency room. Carter and…

Corday’s ordeal, caused by the recent infection-related deaths of several of her patients, worsens when she is closely observed by a stern taskmaster. Corday is outraged when a county investigator…

Dr. Susan Lewis arrives, looking for work in the Chicago area again. Greene hires her, over Weaver’s objection. Chen nervously attends a risk management review, accompanied by the unforgiving Weaver,…

Much to Ray’s dislike, a surrogate mother in labor doesn’t want to have a C-section and endangers the life of the baby. Meanwhile, Sam tells Luka she and Alex are…

Much to Ray’s dislike, a surrogate mother in labor doesn’t want to have a C-section and endangers the life of the baby. Meanwhile, Sam tells Luka she and Alex are…

A dead man is found inside a human-size hamster ball; the team collaborates on a serial rapist investigation.