Once upon a time, early in the 22nd century, Earth was under a severe attack from Mental's minions and humankind was about to evanish. Sam `Serious` Stone, worlds bravest hero, was sent back in time to change the past and save humankind from total annihilation.
Using the ancient artifact, called the "Time-lock", left on Earth by a long-forgotten race, Sam was teleported back in time into the land of Egypt. There he discovered traces of Sirian civilization and found out about their spaceship, hidden somewhere inside the Solar system.
Notorious Mental, the immortal evil, gathered some of the nastiest creatures in universe to stop Sam. Thousands of beasts stood on Sam's way, together with giant Ugh-Zan III, vicious warlock and one of the toughest Mental's servants.
But standing in Sam's way is not a smart thing to do. After many serious battles Sam defeted Mentals army. Finally, in front of The Great Pyramid, he encountered mighty Ugh-Zan III, and won this glorious battle. From the pyramid, Sam teleported himself onto the Sirian spaceship.
And now, Serious Sam goes to Sirius.
Or, maybe not?