What better way to start of The Ultimate Summer Season Three Premiere, with the Ultimate Crossover? Mal, Evie, Jay, and Carlos travel to New York City in search of a normal teen party. Well, they don't get what they wanted when they crosspaths with the one and only Clary, Izzy, Simon, Alec, and Magnus. Other wise know as the Shadowhunters. But happens when Mal gets mistaken for the chosen one? And through a series of events, The Descendants get in trouble with the Shadowhunters and together they have to out smart one of the most evil villains ever... Valentine.