Ever notice how the very real handicap that is dissociative identity disorder has been wantonly sprinkled into an almost impressively large number of horror films, thrillers, and even comedies with very little understanding as to how it actually manifests in real life? If so, you probably had an issue with Secret Window, and you wouldn't be the only one.
It should be a slam dunk of a movie. Based on a Stephen King short story, it's about a writer named Mort (Johnny Depp in his post-Pirates of the Caribbean prime) who retreats to a cabin in the woods to craft his next book, only to be confronted by a deranged stranger named Shooter (John Turturro) who claims Depp's character plagiarized one of his works. Tensions between the two escalate and eventually turn to violence and murder.
The twist, as you can probably conclude, is that Shooter doesn't exist. He's a result of Mort's DID, which—conveniently—has never manifested in the movie until this moment. Sometimes this twist works, but in Secret Window, it only comes off as uninspired; it's such a coincidence, it derails any suspension of disbelief. Secret Window starts off as a pretty engaging thriller. After that, it just feels like a waste of time.