The Flannan Isles are a group of small uninhabited islands about 30 kilometres west of Lewis, and the lighthouse there became famous in 1900 when its three keepers vanished without explanation. The mystery attracted writers, poets, and conspiracy theorists throughout the 20th century — Wilfred Wilson Gibson's poem "Flannan Isle" brought the story wide attention. The islands and the lighthouse are still accessible, though only by chartered boat from Lewis in calm weather.
From Lewis on a clear day, the islands are visible as a faint silhouette on the western horizon — a reminder that the Outer Hebrides are themselves just the last inhabited outpost before the open Atlantic. Even for those who don't charter a boat, the story hangs over the western coast of Lewis.