After Caroline discovers her 'parents' to be Black Mesa spies, Doug Rattmann hides young Chell in Old Aperture before she's sealed off and presumed dead. Years later, she's back, and her resurfacing could lead to Aperture's downfall. A Portal prequel about what it truly takes to have a shot at redemption.

Caroline was never deleted; she fled from GLaDOS, finding a new body to inhabit and trying to make sense of her new situation. Furthermore, Rattmann was not dead; he was unintentionally preserved, and unintentionally awoken many years later. And GLaDOS was not done; there were still more chambers to be made, elements to be tested, and Science to be done.