In Doom we travel to the year 2046 where scientists of the Union Aerospace Corporation (UAC) in the Olduvai Station on Mars are attacked by an unseen monster. On Earth, a team of eight Marines (Sarge, Reaper, Duke, Destroyer, The Kid, Portman, Goat and Mac), known as the RRTS Hellfighters (Rapid Response Tactical Squad) are prepared to investigate the events.
They are teleported to Mars via a device the "Ark", located at Area 51.
The Marines explore the facility, encountering creatures intent on killing them. As the Marines are killed one by one by creatures that were human, they discover that the UAC Genetic Science Division was testing Chromosome 24, an extra Martian chromosome that makes some superhuman and others monsters.
Dr. Grimm reveals that C24 seems to be "chosing" whether it causes the person infected to be superhuman or a monster.
When one of the mutated scientists escapes the Olduvai Research Facility and reaches Earth, the surviving RRTS members need to follow it through the Ark. When Dr Grimm reveals that C24 chooses, Sarge orders to kill them all. In the fights Sarge is infected and Reaper is fataly wounded, left to die...
To save his life, his sister, Dr Samantha Grimm, injects him with C24. When he awakens, he is superhuman with enhanced strength and healing abilities. After killing an array of zombies he is faced with a transforming Sarge, and they have to settle the score, man to ... monster.
Doom 2: Site B
On Earth in the year 2051, in the Union Aerospace Corporation Headquarters (UACH), located in Area 51, the Board of Directors decide mission "Olduvai Site B" is a go.
After defeating Sarge five years earlier, John Grimm ("Reaper") destroyed all data about Olduvai's Genetic Science Division's research into Chromosome 24 and was discharged with honor. Keeping certain data about C24 a secret between him and his sister, Dr Samantha Grimm, they were the only survivors of the Olduvai-Incident in 2046.
After multiple failures to restore the Ark, the UAC Space Scientists Team decide the only way to explore Olduvai Site B is by going to Mars the traditional way. After 5 years of preparations, a new RRTS team of 11 Hellfighters is hereby assembled and prepared to travel to Mars, while remaining in hyper sleep mode for 9 months.
When hearing about new and unknown intelligent activity on Olduvai "Site B", and knowing there was no human left on Mars, Reaper decides to get involved. Fearing that a few scientists or monsters left behind will find a way to travel to Earth, after restoring the Ark on Mars Olduvai Research Facility "A", he decides that this time, ... hé will have to finish them off once and for all.
Believing they are on a search and destroy mission, John Reaper is betrayed by the UAC Board of Directors and by the RRTS team on arrival. The team has the orders to bring back one of the creatures alive and disregards Reapers knowledge about C24 and the dangers of infection for all humanity.
After an outbreak of violence between the RRTS and a superintelligent surviving mutated scientist in Olduvai Site B, John is fataly wounded and left behind. The few remaining RRTS members leave for Earth, carrying in the belly of their ship's cargo, the captured mutant.
Thinking about his sister, John realises that his only chances are an Ark travel... and he starts to restore the uplink. When he succeeds a month later, he travels through the Ark, destroying Olduvai forever. Upon his arrival on Earth he is captured by the UAC and placed in a holding cell, untill the spaceship returns.
When the ship lands at Area 51, 8 months later and opens her doors, all hell breaks loose...
