By the 22nd century, humanity had used ancient found in Egypt to colonize the stars. However, this expansion drew the attention of Mental, whose infinite hordes of monsters began a systematic extermination of the human race. After years of losing every battle from Alpha Centauri back to Earth, humanity is on the brink of extinction. The First Encounter: Ancient Egypt
The story continues immediately after the first game. While Sam is traveling through space, his ship is struck by a "bus" full of Croteam developers (a fourth-wall-breaking joke), causing him to crash back to Earth—this time in the of South America. Serious Sam HD: The Second Encounter General Discussions
Sam reaches the Great Pyramid to activate a Sirian starship. He defeats Ugh-Zan III , a four-armed giant and Mental's most powerful general, by luring him into a powerful energy beam.
World leaders decide to use the , a Sirian relic, to send a single soldier back to ancient Egypt. The goal: use the past to change the future and stop Mental's invasion before it ever truly begins.
The story of follows Sam "Serious" Stone, humanity's last hope in a desperate war against a god-like extraterrestrial overlord named Mental . The Last Stand of Humanity