Carter trains Benton's new med student, Deb Chen, while Carol has her hands full with an emotionally challenged patient who's obsessed with colors. A sociologist provokes people so he can measure their reaction times for a study. Kayson brings charges against Susan in the Vennerbeck death, leading Morgenstern to question her assertiveness. Benton and Walt hunt for Peter's missing mother.

Mark is invited to join the staff as an attending physician. Later, he treats a woman with breast cancer, who begs him to kill her. Deb wows Benton with her presentation, leaving Carter in the rear again. A poisonous snake gets loose in the ER. Benton offends Haleh, who spends her day making his job more difficult. The ER gets new crash carts, which are promptly stolen by cardiology.