Once again, Sam Stone must use the Time-Lock to travel back to the past to defeat Mental's Horde and save humanity's future.
During this mission, Sam has a new enemy. Since Mental itself is on vacation, its horde is now under command of General Maxilla, who readies the horde (often unsuccessfully) for battle.
 Game Play
Double D will be a side-scrolling 2D shooter developed in the style and spirit of previous Serious Sam games, with features such as combat against large amounts of varied enemies with a selection of varied weapons, over many different locations.
- One gun sometimes not enough? Two still too wimpy? Try firing all your guns at once with the Gun Stacker system!
- New Enemies in glorious 2D! Serious Sam Double D brings the crazy with new creatures like the flying Chimputee and the Etanoh Salvo Spider!
- Porta Pad technology! A portable jump pad which Sam can place on the ground for higher jumps for those hard-to-reach places.