When Boris sends a jet to whisk Hank away to his "winter residence," Hank is expecting a quick trip to Manhattan. Instead, he and Evan find themselves landing on a very different island: Cuba. A local geneticist named Dr. Casseras has diagnosed Boris, and, eager to participate in her new clinical trial, he has brought Hank to Cuba to evaluate and prepare him for the treatment. Hank urges his patient to exercise caution, but Boris and the beautiful Dr. Casseras - whose relationship, it appears, may be more than just professional - have other ideas.

With Hank occupied, Evan is forced to make his own fun; luckily, it's a field he happens to be an expert in. He soon finds a scuba partner in a comely Canadian named Mindy, who is in Cuba vacationing with some friends. The two hit it off, but when Mindy's friend has a medical crisis, it's Hank whom she turns to for help.

Back at home, Divya is left to deal with Hank's temporary replacement, an ambitious and abrasive young doctor named Emily Peck. The two women clash over treatment styles, patient care, and... just about everything else. But with the Lawson brothers experiencing an unforeseen delay in their return to the Hamptons, Divya might not be rid of Dr. Peck quite as soon as she'd hoped.