To keep the peace between the Shadowhunters and the Downworlders, a treaty designates an intermarriage between the two groups every seven years. Alec isn't exactly happy to be chosen, but then he finds out that his intended is nothing like what anyone expected.

After the events with Deucalion and Jennifer Blake, Derek goes on a search for his biological family. He, Stiles, and Cora head to New York City to try to find the family he doesn’t remember. It turns out that there was a lot to his adoption that he never knew.