Dead Space: Extraction takes place before the events of Dead Space and during the same time as the animated film Dead Space: Downfall.[4] It revolves around a group of space colonists from the Aegis VII colony fighting against the infection of Necromorphs created when the Red Marker is removed. Necromorphs are the re-animated, mutated corpses of dead humans and serve as the major antagonists of the game. The game also introduces a new female protagonist to the series.[5]
The story begins with a small crew of miners, among them a man named Sam Caldwell, who are helping to extract the Red Marker from Aegis VII. The crew begins to suffer hallucinations, including Sam, who is forced to kill many others in self-defense. Before he can escape, a P-Sec squad arrives and kills him.
Some time later, Detective Nathan McNeill, who is working on the case file of the rampage, meets an old friend, Gabriel Weller, now serving on the Ishimura, charged with retrieving suicide victims from the colony's morgue. Upon arrival, they discover that the bodies have vanished, and they are soon attacked by crazed colonists, finding that this outbreak has spread to the entire colony. Soon after, they begin to encounter Necromorphs. They also discover Lexine Murdoch, Sam's girlfriend (as seen in a short prologue), who McNeill recognizes from the report. They agree to take her to safety. The group races to find a shuttle, and see one take off, then lose altitude and crash, apparently destroying the rest of the shuttles. Noticing a man amidst the rubble, they find a man named Warren Eckhardt, an executive from the mining company, who informs them that he came in on a surveying shuttle near the Megavents, and that they can escape that way. After fighting through the Megavents, they come across the surveying shuttle and attempt to use it to escape to the Ishimura. The Hive Mind (the final boss from the original Dead Space) attacks the ship, but they are able to escape.
The survey shuttle exits Aegis VII's atmosphere. Eckhardt tries to hail the Ishimura but is cut off when Weller begins entering the debris field up by the planetcrack. Nathan is set on using the defense gun to keep the Vestri safe as she swiftly dodges meteorites and asteroid fragments. After the Vestri and several other shuttles lay eye on the Ishimura it hails them and warns them all to return to the surface immediately. Weller and others refuse to return to the infested colony. Another shuttle pilot tries to approach the Ishimura and is shot down immediately by one of the ships many A.D.S cannons. The burning remains of the shuttle twists backwards and damages the Vestris main thrusters. Nathan defends the ship as it twists and turns closer to the Ishimuras hull. When the Vestri is out of range of the guns it is sent on a fast crash course into one of the Ishimuras many pillars and towers. Nathan is ejected from the turret and confronts weller and Eckhardt in the main hold. Lexine's location aboard the shuttle is unknown by your character the entire flight, though she appears next to Weller after Nathan and his discussion. The group evacuates the Vestri and space walk to a nearby airlock. Nathan hacks it and the group gain access to the Ishimura. After entering the Ishimura the group discovers the ship itself is infested with Necromorphs. As they attempt to move to the bridge, which they believe will be safer, they are discovered by a security team and Nathan is knocked out. Some time later, Nathan wakes up to find he, Weller and Eckhardt are quarantined in the ship's medical bay, along with Lexine, who has finished undergoing some medical testing under the hand of the ship's senior medical officer, Nicole Brennan. While McNeill and Eckhardt are released from their pods, Weller is stuck when the quarantine is tripped, and McNeill has to repair the system before Weller can be freed as well. He does, and heads to the Morgue to wait for the others, where he discovers the body of Captain Matthius. The group, reunited, moves through the ship, eventually finding more security officers barricading themselves in a corridor. Nicole elects to stay behind with them in case anyone else arrives, and the rest of the group continues on to find a squad missing in the Engineering Deck. Before they arrive, however, the group falls into the sewage system.
In the sewage system, Lexine is attacked by Swarmers and is pulled into a water tank. Eckhardt and McNeill attempt to save her, but she is nowhere to be found, and they assume she has died. In the Hydroponics section, they encounter Dr. Catherine Howel, who is attacked by a giant Necromorph and flees; the others are able to defeat it.
Howel continues through the ship, eventually encountering Lexine, who has somehow survived. Lexine urges her to help find her friends, but Howel believes they are dead and says they must simply find a way to safety. After surviving a Brute attack, the two find McNeill, Eckhardt, and Weller, still alive. McNeill, Weller, and Lexine continue on while Howel attempts to shut down the sewerage system, guarded by Eckhardt. Howel accuses Eckhardt of staffing the Ishimura with Unitologists before the ship left for Aegis VII. Before Eckhardt can retort, the two are attacked by a giant Necromorph tentacle. Eckhardt flees, locking the door behind him, allowing the Necromorph to kill Howel.
When he finds the others, Eckhardt lies and says Howel died to fight off a swarm of Necromorphs. Weller is suspicious, but they are interrupted by more Necromorphs and forced to flee. In order to search for a shuttle and a way off the Ishimura, McNeill and Lexine split up from Weller and Eckhardt to search multiple shuttle bays. Weller and Eckhardt find a shuttle, but it is connected by several gravity tethers, which Weller disables. When he returns, he finds Eckhardt finishing a recording of a message to a member of the Church of Unitology. Weller watches the message; Eckhardt says that he was sent to find a person who was immune to the effects of the Marker, and who could protect others from its effects as well, and he believes that Lexine is that person. He intends to return her to the Church. Before Weller can do anything, Eckhardt shoots him and tells him that Lexine can never know what the Church is intending to do. Suddenly, he is attacked and killed by a Necromorph.
Meanwhile, Lexine and McNeill are heading to Weller's position, during which time they see a video image of Nicole committing suicide. They find Weller, who tells them Eckhardt killed Howel but doesn't say why. Weller tells them the shuttle is ready to fly, but that the Ishimura's cannons are preventing them from leaving, and that they must be shut down. McNeill heads to the bridge and hacks the ADS system, but has to shut down the power manually at the cannon itself. He does so; while returning along the ship's hull, he is attacked by another large Necromorph, which he kills. Before he can escape, the creature shoots a spike through his arm, forcing him to amputate it. Weller and Lexine, meanwhile, are attempting to protect the shuttle from waves of Necromorphs - in the nick of time, McNeill arrives and the three manage to escape. As they do, they hear a transmission from the USG Kellion. Lexine tries to warn them away but they do not receive the message.
In an epilogue, we see a Necromorph attacking a defenseless Lexine from behind on the shuttle, and she screams as it lunges at her. Her fate, as well as those of the others on the ship, is left unclear.