Because Carl's past has finally caught up with him. The young woman driving the car is convinced her passenger is guilty, and that he's killed, other young women. Including her sister Rachel. Now they're following the trail of his photographs, his clues, his alleged crimes. To see if he remembers any of it. Confesses to any of it. To discover what really happened to Rachel. Has Carl truly forgotten what he did or is he just pretending? Perhaps he's guilty of nothing and she's the liar. Either way in driving him into the Texan wilderness she's taking a terrible risk. For if Carl really is a serial killer, she's alone in the most dangerous place of all . . .