The game begins where Thomas receives a letter from Emily, who invites him to come to her castle for a cake she has baked for him. Thomas arrives at Emily's castle, along with Edward and James. The trio disappear as they enter the castle, and Salty, the game's camera operator, informs Peter Sam, of the disappearance. Percy explores Emily's castle to find Thomas, Edward, James, and Emily. Scattered throughout the castle are paintings and secret walls, which act as portals to other worlds where Diesel 10 and his minions guard the Power Stars. After recovering most of the power stars and defeating Diesel 10's minions, Peter Sam acquires keys that access other areas of the castle, where he finds Mario and his friends captured. First, Peter Sam defeats Smudger and frees Thomas as they continue searching the castle to find more Power Stars. Second, Thomas defeats Hector and frees Edward who uses "invisibility power" to get James's key. Third, Edward defeats George and frees James using the key. Thomas and his friends then tackle three obstacle courses, with each ensuing a battle with Diesel 10. After defeating him twice, they receive a key that opens even more levels of the castle. After collecting 150 power stars, Thomas and his friends reach the highest area of the castle, where they ensue a final battle against Diesel 10. Eventually, after Diesel 10s defeat, Thomas and his friends return to Emily's castle, where they free Emily from a stained-glass window above the entrance. As a reward for saving Emily, she kisses Thomas on the nose and bakes the cake she had promised. The game ends when Thomas, Edward, Emily, Peter Sam, and James wave goodbye as Salty films and then flies away. A photo with Emily's cake then appears.