After Serious Sam The First Encounter, Serious Sam The Second Encounter continues the story.
After Serious Sam got onto the starship you would imagine that he got to Sirius and defeated Mental, but no! His ship got hit by a small space-bus and he crash-lands on Earth, in Central America, but in the Mayan age. But the Sirians left a spare ship on Earth, but in another age, different to the one Sam is in. So he goes through Mesoamerica during the Mayan age, and finds the first time-gate, but it was guarded by Kukulkan, a Mayan god of wind, under the command of... Mental.
Then he got teleported to Mesopotamia where he got into the Tower of Babel, and faced another boss. It was the "Exotech Larva", it was a monster larva, half biological and half robotic, armed with hi-tech weapons. This monster was produced by... Mental.
And finally Medieval Europe, where the ship is, and the final obstacle between Sam and the ship to Sirius is "Mordekai the Summoner" he is a un-dead creature revived and serving... Mental.
After the great battle against the Summoner, Sam enters the cathedral and holds the Holy Grail in his hands and confessed his sins in a booth... ... to Mental. And he says that he will get Mental.
END of game- Serious Sam the Second Encounter