Serious Sam: Next Encounter takes place after the first two Serious Sam games.
In this one, the hero, Sam, steps into a time machine and is teleported back to ancient Rome. Mental's forces are waiting for him there when he arrives.
The weapons in this game are clones of the ones in the other games of the series, just with different names. This game is also a console exclusive for Gamecube and Playstation 2. It is was not developed by Croteam, but rather Climax. The games are identical in style and graphics, however.