Australian director and cowriter James Wan's debut feature is a twisted, squirm-inducingly nasty bit of work, which isn't a criticism because that's exactly what he and cowriter Leigh Whannell had in mind. Two strangers, middle-aged Dr. Lawrence Gordon (Cary Elwes) and seething slacker Adam (Whannell), awake at opposite ends of a large, dirty, industrial bathroom. Neither remembers how he got there. Each is chained by his ankle to a pipe. A man's corpse lies on the floor leaking blood, just out of reach, clutching a microcassette recorder and a gun. Lawrence and Adam soon discover that each of them has a personal message on the tape from a serial killer nicknamed "Ji...