Mario is Missing! is an educational video game released for the PC in 1992 and then for the Nintendo Entertainment System and Super Nintendo Entertainment System in 1993. The game was developed by The Software Toolworks (Raidcal Entertainment for the SNES and PC versions) and published by Mindscape. It is the first game where Luigi is the protagonist and it is the only solo adventure for Luigi until 2001 when Luigi's Mansion is released on the Nintendo GameCube.
Taken directly from the Super Nintendo Entertainment System version's manual;
Oh no! Bowser and his bad boys are back to a life of crime. This time, it's not Mario World -- it's your world! From his Antarctic castle, Bowser hustles his cold-blooded crew of cantankerous Koopas into his powerful Passcode Operated Remote Transport And Larceny System (PORTALS). The twisted turtles transport themselves throughout the globe, where celebrated cities suffer shocking crime waves, as turtles trash landmarks and loot ancient artifacts. With dough from his slimy sales, Bowser hoards hair dryers from the Hafta-Havit Hotline. His plot? Melt Antarctica and flood the planet! Whoa!