A pretty impressive horror film in the form of a documentary, supposedly made up of footage shot by three film students on a trek through Maryland’s Black Hills Forest to investigate legends about a witch. What gives the film much of its force and its mounting sense of queasy uncertainty is its narrative method, which ensures that we know no more about the proceedings than the characters do and that our imaginations play as active and ambiguous a role as theirs. Written, directed, and edited by Daniel Myrick and Eduardo Sanchez; with Heather Donohue, Michael Williams, and Joshua Leonard, all of whom do fine jobs. (JR)