Phineas and Ferb build a time machine and invite their friends for a journey across time. When Candace intervenes and cause a malfuntion, pieces of the time machine scatter across time and traps the kids in the stone age. With each piece they collect they gain access to another time period, so it's up to them to rebuild the time machine and get back home. Journey through many glorious moments in time, from the beginning of time, to the middle ages, even into the future. What will become of our heroes, only time will tell.