Just Before Dawn (1981)

Just Before Dawn (1981) Five campers arrive in the mountains to examine some property they have bought, but are warned by the forest ranger Roy McLean that a huge machete-wielding maniac has been terrorising the area. Ignoring the warnings, they set up camp, and start disappearing one by one. If that sounds too run-of-the-mill, there's a genuinely shocking plot twist half-way through...