Hal is snatched from land by merman prince Ken and taken to the undersea kingdom, where he regains lost memories and rekindles their romance after mending old misunderstandings. Ken’s scorned fiancé Niah — a secret dark sorcerer who once tricked Hal into fleeing — plots revenge with pirate Jack to destroy the merman clan. Hal claims his birthright as palace guardian, wields the legendary trident, and helps Ken defeat their foes...