On the remote island of Selkie, the royal Historian, Hovar, is on a mission to investigate the ancient ruins of the island. However, his task is threatened by the many dangerous wild beasts of the island, and he is running out of ammunition to keep them away. Man-At-Arms has invented a sonic device called the VHO (Variable High-frequency Oscillator) which can emit high pitched sounds that will drive animals away. Adam and Teela set sail to Selkie Island with the VHO- but on the way, their ship is attacked by Merman, who sets the mighty sea demon called the Kraken on them... captures Teela, and steals the VHO! Adam transforms into He-Man, but can he save Teela from Merman's clutches, and recover the VHO and get it to Selkie Island, before Hovar's time runs out?