In 1944, a commandos team consist of two soldiers are sent to the Channel Islands, which are occupied by the German Army, to do their mission of creating sabotage and distraction. Using kayaks they land on the coast and find that the island is lack of guard. They soon discovers the Nazi occult conspiracy to unleash demonic forces to win the war.
By keeping the action confined to the tunnels and cells of the blockhouse, Campion creates a claustrophobic setting, but for all the gore and demonic transmogrification, there's a distinct lack of chills and frights.
For all its gore, The Devil's Rock is an undercooked chiller, but it cleverly uses the conventional tropes of diabolism to comment on the horrors of war.