When a commuter ship capsizes, our ED finds itself underwater as they struggle to treat the influx of new patients and deal with the bold new employees taking charge.

Dr. Lenox continues to rankle Archer as the two tackle their new roles. Ripley faces possible suspension over what really happened to Pawel, and upstairs, Goodwin is forced to make layoffs.

Hannah treats a woman whose undiagnosed condition threatens the lives of both her and her unborn child. Goodwin receives a chilling message while battling the hospital higher-ups.

A familiar face returns to the E.D. Ripley and Charles treat a woman with a rare disorder. Frost suspects that his patient’s father is lying about his daughter’s condition.

Halloween chaos takes over the E.D. Hannah helps a pregnant woman with an autistic son. Charles clashes with nurse Jackie on a psych case.

Chicago P.D. steps up Goodwin’s security after she’s threatened online by a former employee. Archer and Frost treat victims from a disciplinary camp injured during a rockslide. Maggie gets roped into delivering a high schooler’s baby.

Ripley and Frost uncover shocking information that conflicts with their patient’s DNR. Hannah facilitates an unexpected reunion. The tension between Archer and Lenox comes to a head.

Goodwin’s troubles persist. Charles clashes with his former resident over a depressed patient. Lenox and Ripley treat a car accident victim who recently reunited with his college sweetheart.

The team fights to save the life of one of their own. Frost and Abrams butt heads with their patient. Dr. Charles and Dr. Reese continue to clash over a patient, dredging up unresolved issues between them.

An army of surgeons prepare to separate conjoined twins. Hannah reconnects with someone from her past. Archer treats a tyrannical boss with a heart problem.