5 Years Ago:

Soon after defeating Tabuu and returning Peace to "This World", Mario and the other Trophies discover a Rift in the Space-Time Continuum where the Isle of Ancients used to be. Curious, they travel through the Rift and find themselves scattered in different Worlds. Mario, Luigi, Peach, Yoshi, Wario, and Bowser wake up in a Land called the Mushroom Kingdom. Peach is soon thought to be the great Queen of the Mushroom Kingdom, gone missing several Years ago. Mario & Luigi are thought to be the great Heroes that protect the Mushroom Kingdom. Yoshi is thought to be Mario & Luigi's Noble Steed. Bowser & Wario are thought to be the great Villains that are always trying to take over the Kingdom. 5 Years go by, with the Newcomers from "This World" playing the Parts of the 6 People they were mistaken for.

The Present:

5 Years have gone by since the residents of "This World" arrived in the Mushroom Kingdom. It seems that Bowser is hiding at his Volcano Home plotting his next attack. Mario & Luigi are at their Home watching TV, when a Breaking News story interrupts every TV Show. Apparently there is a Meteor Warning. Mario & Luigi look outside to see, and the Meteor crashes into Bowser's Volcano Home of in the Distance. A Huge Purple Ball starts expanding behind Bowser's Volcano, which Mario immediately recognizes as Subspace. Remembering the devastating effects of Subspace, Mario runs off to check on Peach, while Luigi hides under his Bed.

Peach's Hideout:

Mario arrives at the place where Peach is to go in case of an Emergency, and finds her getting kidnapped by none other than Subspace Mario! With Peach captured and the Subspace Ball growing, Mario has no choice but to track down Bowser and stop his Evil Plans once and for all.