The theft of the Primal Stones from Kong Island threatens to awaken the ancient demon Chiros. Lua journeys alone to Chiros' ruined temple in an attempt to imprison him. She is captured and brainwashed by Harpy, one of Chiros' servants. They journey to the Island's volcano and set the demon free. Jason, Kong, and Tann arrive and Chiros awakens the monster Ominous to stop them. Jason merges with Kong and confronts him. In the fight Kong's anger transforms him into the gigantic Mega-Kong. He easily defeats Ominous forcing Chiros to retreat.