Ed (Jon Voight), Lewis (Burt Reynolds), Bobby (Ned Beatty) and Drew (Ronny Cox) decide to canoe down a fictional river before it is flooded to make way for a damn and lake.
In order to get home safely before the big game on Sunday they must overcome unfriendly locals while trying to survive nature's wrath in the river's raging rapids.
Rather than delivering a story that flows, Deliverance prides itself on leave the main characters in a whole number of morally ambiguous situations that leaves sticking points while they decide what to do.
Despite there being very little blood and guts, Deliverance can easily be compared to a horror film because parts of the film cross a certain line of disturbance in such a way that it is completely unexpected and, when it does happen, you can't help but look away and cringe at what might be happening on the screen in front of you.
For me, the most bizarre thing is how Reynold's character was handled - surely in any clichéd film the main protagonist would be immune to such horrors surrounding the group. But no, his character is, if anything, the most foolhardy of them all serving a reminder to how easily nature can turn - even on those that worship it.
Horrifying - without horror. Perhaps disturbing should cover it.