As Joel and Ethan Coen demonstrated with their fraudulent “based on a true story” caption in Fargo, the supposed veracity of a movie's plot can obscure the truth more than reveal it. The same caption appears in this thriller adapted from an Armistead Maupin novel, in which a radio personality (Robin Williams) who's recently broken up with his male lover becomes obsessed with a young fan (Rory Culkin) who's been calling him but who may be the invention of a blind woman (Toni Collette) claiming to be his mother. It's a relief to see Williams underplaying for a change and letting us fill in the blanks, but the movie's suggestiveness gives way to a certain thinness and lassitude. Patrick Stettner directed; with Joe Morton, Bobby Cannavale, and Sandra Oh. R, 82 min.