The attending surgeons and interns work together to solve a medical mystery when a college kid comes in with what first looks like food poisoning but has escalating and dire complications. Meanwhile, Jo spends her day off with Bailey.

It's Halloween night at Grey Sloan Memorial. Meredith and Nick try to spend some alone time together; Levi is stressed due to overworking, and Winston and Owen have the interns practice trauma training on a real cadaver.