Thrillers have always been one of the more contrived forms, but there are limits. Within the world the story creates, the logic must make basic sense.
This film has such a poor set up that I almost walked out. The hero meets a stranger in a bathroom on a superhighway. The stranger claims to be an old school acquanence, but the hero has no memory of him. Yet he invites the man and his girlfriend to their country house, then to stay overnight. Then he accepts a brand new car from the stranger. This is not just unbelievable, it's stupid, and there's nothing that angers an audience more than a stupid hero.
Throughout the movie there isn't a peep about motive from anyone. None of this bizarre behavior makes any sense.
The only explanation that has any weight is that the stranger is a figment of the hero's imagination. But notice that is a classic cop out. If the hero is crazy then anything is allowed and the story doesn't have to make sense. You just end up with a really pissed off audience that doesn't like to waste two hours watching lies.