It's not even close to good, but it's not as bad as the IMDB and Tomatometer ratings indicate. A Mrs. Salad pick, because she loooves Simon Baker in The Mentalist TV series.
But here, Simon Baker is not The Mentalist. Instead, he is The Lodger, a semi-creepy cipher who shows up at the door of the Bunting household in Hollywood, looking to rent out the guest house out in the back.
Unfortunately, at the same time, serial hooker homicides are afoot in Hollywood. The detectives assigned to the case (Manning and Wilkinson, played by Alfred Molina and Shane West respectively) can't help but notice the new murders mirror some "solved" homicides for which a guy named Rodriguez was executed a number of years back. And (eventually) they notice parallels with London's Jack the Ripper.
What's going on? Well, it's one of those movies where they throw up a lot of red herrings. The killer might, after all, be The Lodger; he's certainly an odd duck. But Mrs. Bunting (played by Hope Davis) is kind of quirky too. Her husband keeps telling her to take her pills—what's that all about? And what about her husband, who conveniently is out of the house most evenings?
Also Detective Manning has some dysfunctional relationships of his own: his wife is in the loony bin, and his daughter blames and despises him. And he's also put on a pile of weight since he was Doc Ock in Spider-Man 2. And he sent that guy Rodriguez to the … chair? gas chamber? Wherever they execute guys in California these days.
So there are a lot of potential suspects, and eventually it all seems to be sorted out at the end,… or is it? (One of the problems with red-herring-laden movies is that you really should play fair with the viewer and show how all those herrings make sense in retrospect. As near as I can tell, this movie doesn't do that.)
In the nothing-new-under-the-sun department: this is the fifth movie remake of the original source material, a 1913 novel by Marie Belloc Lowndes. (The 1927 silent version was directed by Alfred Hitchcock.)