This action drama returns from an agonizingly long hiatus (at least for its fans) with "Train in Vain," a crossover event with sister show "Grey's Anatomy." As the action resumes, Drs. Carina and DeLuca (Stefania Spampinato, Giacomo Gianniotti) are on the trail of Opal (guest star Stephanie Kurtzuba), who is suspected of sex trafficking. Elsewhere, Maya (Danielle Savre) leaves Andy (Jaina Lee Ortiz) in charge of the yearly inspection, while Vic and Dean (Barrett Doss, Okieriete Onaodowan) struggle to cope with the fallout from Dean's arrest. Boris Kodjoe also stars.