In the year 1993, Bowser uses a time machine, traveling backwards to different points in human history and stealing significant artifacts to place in his personal museum inside his castle. With his collection nearly completed, Bowser gloats that not even Mario can stop him now. Mario realizes that history will change forever if he does nothing, so it's up to Mario to use Bowser's own device against him by returning the artifacts to their proper places in time. The home console releases add that Bowser plans to destroy his time machine (called a Timulator in console manuals), deliberately planning to irreversibly damage history and send the world back to the Dark Ages. In the NES game, Bowser's Museum has been fully built and already established itself with history's greatest artifacts. Yoshi joins Mario in his quest to stop Bowser's plot, but instead gets captured when he scouts ahead. In addition to fixing the timeline, Mario must also rescue Yoshi from peril.