after killing glados and escaping aperture science laboratories, chell, the protagonist of "portal", is taken back to the labs and placed in suspended animation for many years. while she sleeps, the laboratories become more and more run down, because no one is there to take care of them. once she wakes up, a small, dim-witted robot, known as a core, named wheatley tries to help her escape the building. in the process, he accidentally reactivates glados, who, still angry with chell for killing her, forces chell to perform tests similar to the ones she performed in "portal".