“Rattlesnake” (** out of four) was a tepid melodrama about a young mother (Carmen Ejogo) whose daughter is bit by a poisonous rattlesnake along a desolate strand of road in the SouthWest. She accepts the help of a mysterious woman who gives her daughter rejuvenating powers but subsequently finds that she has made a deal with the devil and has to kill an innocent person for this deal to be finalized. Intriguing story keeps you tensely in its grip for a while but then wanders off and loses its grip as story unfolds in too many different directions. Ejogo’s palpable and believable performance make this worth watching, at least for a little while.