(Peter Carter, 1977)
Brilliantly compact and elemental, and genuinely chilling to boot, this is far from just another "Deliverance" rip-off, although it's that too. Every one of the five doctors on this camping trip from hell is a total pain in the ass, carrying years of interpersonal baggage which is implied with the barest quantity of exposition. We learn just enough about their immersion in first-world problems to fully feel their disorientation as a mysterious enemy targets them with shocking speed and unpredictability. Because the assailant remains unknowable until the very end, the film keeps an appropriate focus on the rapidly deteriorating psychology of the victims. While it would have been even more powerful if the killer remained totally ambiguous, the big reveal is murky enough and leaves enough unanswered questions - and is an impressive enough set piece in its own right - that one hesitates to complain. Most importantly, the performances are all brilliant, with a hauntingly childish vulnerability lurking just beneath their defensive belligerence. The depth of craft in writing, direction, and cinematography is comparable, allowing for far more human insight than you expect from what is essentially a prototypical slasher film. A hard one to shake off.