Steve and Gabrielle fight to save the life of a worker who has suffered long-term exposure to chemicals. Elsewhere, Von and Charlotte treat the worker's boss, who is suffering similar but lesser symptoms. Does he know more than he's telling? Then, Jack faces an internal investigation about the death of one of his patients, only to find an even bigger challenge awaiting him when he returns to the ED and has to face his dead patient's widow. Dan is in denial about Erica's disappearance. Mike's relationship with Juliet is going well, but she issues him a subtle challenge — time to step outside his comfort zone.