The movie opens with Doug Quaid having a dream about himself and a brunette woman, walking together on the surface of Mars. One of the arguments that the movie makes that the events of Total Recall actually happen is based around the character of Melina, played by Rachel Ticotin. Even the girl's face that he sees looks just like the one he eventually runs into, and has a previous relationship with, on Mars. The alien artifact that creates the breathable atmosphere looks exactly like what Quaid looked at in a monitor back at Rekall. Everything that we see here, which takes place prior to Quaid going under, comes back later in the movie. They also ask him about the sort of woman he wants to meet, as that's part of the package. In addition, the technicians begin to show Doug some Martian artifacts in order to get him acclimated to the things he will experience in his memory. Quaid has already gone under for the procedure which means we can't necessarily take this statement as fact. However, the truth is that by this point we're already past the point of no return. The movie says fairly clearly that Quaid's outburst, and his claims that his 'cover' is being blown, cannot be the result of the Ego Trip, because they had not implanted it yet. It's at this moment that the movie either shifts from 'reality' to 'dream state,' or that Quaid's true memories come out. That's the name that the Rekall company gives to the memory option that allows Douglas Quaid to believe he was a secret agent. The key moment in Total Recall is the Ego Trip.

Total Recall by Arnold Schwarzenegger