Science teacher Ryland Grace wakes up on a spaceship light years from home with no recollection of who he is or how he got there. As his memory returns, he begins to uncover his mission: solve the riddle of the mysterious substance causing the sun to die out. He must call on his scientific knowledge and unorthodox ideas to save everything on Earth from extinction.

In this conclusion of the long running series it finally happens: Kelly and Zack will marry. Zack's parents are against the early commitment and Kelly's parents can't afford it, so only the gang travels to Las Vegas for the wedding. However, before the wedding can happen, they have to live through many adventures, including Zack losing his hard earned money, Kelly becoming jealous and Slater being chased by mobsters.