The Flannan Isles lighthouse keepers

The keepers of the Flannan Isles lighthouse were found missing on 26 December 1900 when the relief ship Hesperus arrived. Newspapers of the time offered several supernatural explanations.

National Records of Scotland gives this account. A steamer passing the Flannan Isles lighthouse around midnight on 15 December 1900 saw that the light was dark and reported it on reaching port. The Commissioners heard nothing of it. The keepers' absence came to light on 26 December 1900, when the lighthouse tender Hesperus made its routine visit.

History Hit adds detail. On 20 December Hesperus made an attempt, and bad weather turned it back. It reached the island at about noon on 26 December. Its captain, Jim Harvie, sounded the ship's horn and set off a flare to alert the keepers, and nobody answered. Wikipedia records that no bodies were ever found.

Speculation followed in the newspapers and periodicals of the day. Wikipedia lists the stories: that a sea serpent took the men, that they hired a ship to start new lives elsewhere, that foreign spies abducted them, and that a boat full of ghosts brought about their end. Wikipedia says local opinion widely blamed the "Phantom of the Seven Hunters". These are later tellings, and Wikipedia calls them implausible.