Calvin Willeford and his best friend, Kathy, must have nerves of steel as they explore the spooky old Diefenbacher house. They find green blood and hear scratchy noises on the floor, but they don't see anything. Calvin and Kathy are sure they have come across more bumbling alien tourists whose equipment has malfunctioned. Then they meet Dandelion, who seems to be an ordinary yellow cat. Actually she's a friendly alien—an interstellar seret agent—and she's in East Gradwohl to stop her enemies from interfering with Earth. But when Calvin's mother is kidnapped by the evil aliens, all of Dandelion's superior powers suddenly malfunction. How can Calvin and Kathy rescue his mother from these horrible creatures?