From the Super Mario Wiki, the Mario encyclopedia
Wario's Scheme (also referred to as Tricksters Episode 2 and Tricksters 2) is the second Tricksters episode in the Story Mode of the Nintendo 3DS version of Mario & Sonic at the London 2012 Olympic Games. The episode is unlocked after completing The Secret of the Fog, and unlocks Stop Dr. Eggman! once it and Waluigi's Ambition are completed. This episode, along with the other Tricksters and Wild Ones episodes, must be completed to earn the Story Mode 3 badge, and its completion is also required to unlock the Story Mode Cleared badge.
Wario arrives at Eton Dorney and decides that is the perfect place to set up a snack stand, though wants the Phantasmal Fog to clear up. He manages to find a Fog machine and initially thinks that it is broken, as it appears smoke is coming out of it, but figures out that the fog is coming from it and decides to destroy it, aiming to clear the fog. As he prepares to punch the machine, Dr. Eggman arrives and stops him. He explains that the machine belongs to him and tells Wario not to break it and leave, but Wario claims that the fog is driving away business and instead tells Dr. Eggman to leave. Instead of continuing to argue, Dr. Eggman suggests that they settle the dispute with an Olympic Event, which Wario accepts.
Wario beats Dr. Eggman and plans to destroy the machine. Dr. Eggman agrees to let him try, but doubts that Wario could actually destroy the machine. Mario and Toad arrive and see that Wario appears to already have the situation under control and decide to leave it to him. Wario prepares to break the machine, but it disappears before he can do so, causing him to fall to the ground. Dr. Eggman reveals that it was actually a 3D hologram instead of a real machine, and then runs off after noticing Mario and Toad. Toad asks Wario if he is alright, however Wario instead runs after Dr. Eggman, aiming to get some compensation. Mario and Toad follow Dr. Eggman to try to find the real machine.