Ariel gets kidnapped in Nickelodeon Studios, and it's up to her boyfriend, Barley Lightfoot, and best friends Ian Lightfoot and Isabela Madrigal to save her from the clutches of a greedy sea god, King Poseidon, who plans to marry Ariel and make her his queen.
Ariel escapes and hides in Bikini Bottom, then runs away again and ends up in Adventure City, until Mayor Humdinger meets her and forces her to be his bride. Along the way, Barley, Ian and Isabela get help from Ryder and the Paw Patrol to find Ariel and save her from being married to Adventure City's awful mayor.