A doctor approaches Zack and Cody and tells them that they would be ideal for the Gemini Project, a massive project studying the effects of twins.

After making plans to spend spring break with Bailey, Cody takes a job as an intern at a prestigious research firm, breaking his plans and leaving Bailey infuriated and refusing to speak to him. Zack then runs a billion-dollar submarine into Vancouver's seawall causing the equipment to get lost which results Cody being fired from the program and vowing to never speak to Zack again. While there, Dr. Olsen approaches Zack and Cody, telling them that they are perfect for the 'Gemini Project,' a massive project studying the effects of twins. After making much thought, the twins decide to participate, and land themselves among dozens of other twins. In the beginning, all seems normal, but before long, the two suddenly find themselves connected metaphysically in a way they never have been-able to before. If one twin has a thought, the other does as well; including feeling the same pain at the same time. But as their week on the 'Gemini Project' campus goes on, they soon discover that all is not what it seems, and set out to discover just what the project is really about.—Shawn SychoSide

While on spring break, Cody decides to go to a scientific lab because he believes he is helping with the scientific community of twins, so he takes Zack along with him. So they start undergoing scientific experiments (Which is called the Gemini Project)and they soon discover that they are becoming one person, and they have to find a way to defeat the evil professor and escape while they are still two people.—Jaime Pierce