The twins move into their university residence and uncover a cryptic letter that hints of unsolved murder. Leaving Tom to juggle packing crates, Annie, Paul and Joey, set off to investigate, but when another clue is brought to light, Tom joins in the search to expose the body thats been buried for thirty years.
Tom is undergoing a torturous initiation into the engineering fraternity and Annie is having problems in biology. When the professor brings in some rabbits as test subjects, Annies outraged lab partner decided to take matters into his own hands and Tom is called in to help Annie save the student from expulsion.
Tom is coerced into mixing up a batch of fertilizer for the seedlings Annie is germinating for her botany class. When an accident in the lab accelerates the growth of the plants at an alarming rate, Annie is thrilled, until Tom unearths a greenhouse conspiracy.
Tom goes horseback riding with Collette Featherstone and Annie is invited to tag along. Before they know it, they are off on a treasure hunt for a lost time capsule containing a secret Collettes Father would rather have kept buried.
Paul and Joey decide to give all their money away and become hippies, but Nick has other plans for Tom and Annie. He knows of a pyramid money scheme thats guaranteed to make them all rich. As Tom is enticed by the lure of easy money, Annie holds fast in her stand against greed.
Out shopping one day, Tom, Annie, and Nick see a fleeing criminal. A suspect is apprehended, but Annie is certain the police have the wrong man. While Paul and Nick practice for a spaghetti eating contest, Tom and Annies investigation leads them to a web-footed culprit.
On his way to a Fifties revival dance, Tom thinks he sees a ghost in an abandoned house. Spurred on by Annie, Tom gives the house a through search with his scientific equipment that sends Annie on her own investigation of the illusive apparition.
The university computer goes on the fritz and the twins decide to find out why, Armed with software and security codes, Tom traces the footprints of a hacker bent on crashing the system in a countdown to technological chaos.
A foulup almost causes Annie to miss her trip to Italy, but a friendly travel agent solves the problem and gets invited to dinner. Nick is jealous and certain the travel agent has ulterior motives and drags Tom into a deadly web of international mystery and intrigue.