Recap / Portal 2 The Surprise

Following the completion of her seventeeth test, Chell enters a dark room ostensibly containing her surprise, but gets only a party blower and a puff of confetti, with GLaDOS revealing her claim of a surprise to be a lie, and reminding Chell that her parents abandoned her.

With the fake surprise over and done with, Chell carries on with her next test and completes it, before taking the elevator to her next one. As the elevator descends, Wheatley makes contact with Chell and tells her that he's managed to talk his way onto a nanobot work crew, before instructing her to complete the next five tests. As Chell begins the third of these though, Wheatley decides to move early, cutting the lights to the chamber and opening a door leading back to the facility's inner workings, allowing Chell to escape.

As Chell runs across the catwalks between test chambers, Wheatley reveals that his plan is to shut down GLaDOS's turret production line and turn off her neurotoxin, thereby allowing the pair to confront the AI without her being able to defend herself. Before they can work on that though, they have to get away from GLaDOS, who first attempts to lure Chell into a test chamber rigged to fill with neurotoxin, then deploys turrets against her, before finally trying to kill her by moving the surrounding test chambers. Chell survives it all, and escapes into another area of the workings.