A young boy in his teens moves into a magnificent home in the mountains of Caguas, Puerto Rico. He hears the story of the builder of the house and how he lost a diamond-studded gold ring. As he becomes determined to find the lost ring, he discovers a world behind a door in a secret tunnel beneath his new home. He meets a very beautiful girl at school. Her name is, Diana. He shares his discovery with Diana and jointly set out to discover the mysteries behind the tunnel's door. The novel is about the adventure that he and his girlfriend, Diana live while taking various trips to the city of Sitnalta. It depicts how they find out of the dangers to humanity posed by mysterious Aliens and how they go about fighting to exterminate them. In the course of the novel, the mysteries of Amelia Earhart's disappearance, the Chupa Cabras, the Giant Squid and several other long-standing mysteries are unravelled. He and Diana enlist the help of Andy, a CIA operative to help tackle the problem of what to do with the new-found knowledge about the Aliens living in close proximity to the Sitnalteans. The way the Sitnalteans live, work, study, their entertainment, their scientific advances, their fishing industry, their museums, are all unraveled in the course of the novel. The way that Victor and Diana, went about putting all their ideas together to get rid of the Aliens, is the basis of the book Sitnalta.