The monster family embarks on a vacation on a luxury monster cruise ship so Drac can take a summer vacation from providing everyone else's vacation at the hotel. It's smooth sailing for Drac's Pack as the monsters indulge in all of the shipboard fun the cruise has to offer, from monster volleyball to exotic excursions, and catching up on their moon tans. But the dream vacation turns into a nightmare when Mavis realises Drac has fallen for the mysterious captain of the ship, Ericka, who hides a dangerous secret that could destroy all of monsterkind.
