It's about a young girl who has sex with her boyfriend, only to then find out that he's passed on a curse to her, a monster that can look like anyone and will keep following her until it eventually catches up with her and kills her. The only way to pass on the curse is to sleep with someone else. However, if "The Follower" is able to kill that person, then it will begin following the girl again.
Overall, a very creepy movie. Right from the beginning though, I came up with a solution for the curse. If the girl were to sleep with a guy, and he slept with a provider, and she with a client, and so on and so on, "The Follower" probably wouldn't have time to go after anyone. Sure enough, this possible scenario is addressed with a scene with 2 streetwalkers. So yeah, not really a movie about hooking, but one that reminded me that I have the hobby on the brain lol.