An engineer named Franco is ordered to repair a computer mainframe deep in the Sprawl, and his girlfriend, an officer named Sarah, goes along with him to protect him. Once the mainframe is repaired the Necromorphs attack, and Franco and Sarah try to escape. The game gives the player options on what path to take, but no matter what the player does, in the end Sarah is killed, either by Franco or something else, and Franco, under secret orders, releases Isaac from his cell.
Levels are made up of three Hacking Minigames; the player has to complete one, two, or three of them to proceed. One minigame is a race to get your computer program to the end before the other programs while avoiding walls that slow you down. The second is a reverse Tower Defense game; you send out unlimited computer bugs to destroy the computer defenses to reach the program before time runs out. The third is a Light and Mirrors Puzzle where you put down mirrors to bounce color-coded lasers so they hit their corresponding computer program thing.
Dead Space: Ignition provides examples of:
- Church of Happyology: One of the paths shows the first real glimpse of the Unitologists in action; a temple on the space station, and their huge cryo-stasis freezers.
- Doomed by Canon: If you played Dead Space 2 Franco is pretty much picked off as soon as he releases Isaac. A necromorph ambushes him and instantly turns him into a necromorph right before Isaac's eyes.
- Fair Cop: Sarah is too hot for law enforcement.
- Gaiden Game: The events of Ignition happen right before Isaac gets out of Stasis in Dead Space 2. How the engineer of the story reaches Isaac is different.
- Guns Are Worthless: Sarah soon realizes that her pistol is worthless against the Necromorphs, but the plasma cutter works a lot better.
- Hacking Minigame: The entire game is just three different ones. One's really more like a race, and one's like the reverse of a Tower Defense game.
- Kill the Cutie/Player Punch: Sarah dies in all of the paths near the end, two of them by Franco's hands. The latter was because he didn't want her to realize that he was receiving orders to get Isaac out of Stasis. In the other two, he's devastated at her loss; apparently his loyalty is highly situational.