In October 1979, a group of seniors from the University of Colorado Boulder Alpine Club resolved to use their week of “winter break” to go hiking and climbing in the remote Branson Pass area in Montana. Eight set out, all of whom were experienced hikers and climbers; two of the students had climbed all of Colorado’s peaks above 14,000ft. in elevation. They left a copy of their itinerary and explicitly requested a search if they had not reported in by November 4.

The small town of Alexander served as their base camp, and local residents later recalled being mildly annoyed by the group’s antics as they purchased supplies and film for their three 35mm and one Super 8 cameras. Just before the ascent, which had Mt. Bronson (14,987ft.) as its goal, two of the club members fell ill with food poisoning. The party was reduced to six and begun its ascent on October 27.

None were ever seen alive again. A storm blew up on the 31st, and on November 4 the Iran Hostage Crisis exploded, greatly hindering the two ill climbers from beginning a search. It wasn’t until November 8 that one was mounted; searchers found the bodies of the climbers, each over a mile from their campsite. Their tent had been torn to pieces, apparently from the inside, and the climbers appeared to have fled into the storm wearing only their underwear or scraps of clothing.

Despite that, they hadn’t all died of exposure. Each had a number of cuts and broken bones, and one of the climbers had a jaw fractured with such violence that her tongue had apparently been bitten off; searchers were unable to locate it. Despite the winter season, searchers reported that the bodies were all quite tan, and then a Geiger counter in a survival kit was accidentally turned on it registered significant radiation from the bodies. No cause for the hikers’ sudden and panicked flight, or their injuries, were ever ascertained.

Once the furor over the hostage crisis died down, the mystery became popular among conspiracy theorists. Most notably, the film that was left in the tent was subsequently developed, and some have claimed to see a tall shadow in the background of several shots in Alexander and at the campsite. The Montana government holds that this so-called “Thin Man” is simply a processing artifact. The final shot in one of the cameras also, according to some, shows lights in the sky or a mysterious form visible behind tearing fabric; skeptics argue that the shot is a simple artifact.