In the 1890s, two lighthouse keepers try to maintain their sanity as they live on a remote and mysterious New England island. As the swing of a foghorn fills the air, taciturn former lumberjack Ephraim Winslow and grizzled lighthouse keeper Thomas Wake set foot on a secluded and lifeless island off the coast of late 19th century New England. Over the next four weeks of hard work and adverse conditions, the two taciturn men, with no company but each other, are forced to endure growing resentment. Then, in a stroke of bad omen, a furious and unending storm traps the keepers on inhospitable volcanic rock, fueling a long period of feral hunger; excruciating pain; manic isolation and horrific alcoholic hallucinations. Now, the insanity is suffocating. Is there still a way out of this invisible prison?