Deep in the jungles of Central America, an archeological expedition to discover a lost city is cursed by a legendary Headless Demon. Thankfully, Miss Mallard and Willard are part of the expedition and they soon learn the lost city is not so lost. Someone has been there before them and is now trying to keep them away. In the middle of the jungle, with no more than bicycle tracks for a clue, Miss Mallard reveals the Headless Demon's true identity and a lost treasure is saved.