The game is the first reboot to the series. Doom 3 is set in 2145 on Mars, where a military-industrial conglomerate has set up a scientific research facility to research into fields such as teleportation, biological research and advanced weapons design. However, the teleportation experiments inadvertently open a gateway to Hell, resulting in a catastrophic invasion by demons. The player, an anonymous space marine, must fight through the base and find a way to stop the demons attacking Mars. Wikipedia.