The plot involves three men tending a lighthouse on an island off the coast of
French Guiana. The rock the lighthouse stands on is dubbed 'Three Skeleton Key', named after a tragedy when three convicts escaping from Cayenne became ship-wrecked on the rock and eventually died of hunger and thirst – the only thing left of them were a heap of bones cleaned off by scavenging birds. The three lighthouse attendants are headkeeper, Itchoua (the eldest of the men), Le Gleo, and the narrator (whose name is never given). An
abandoned ship, infested with ferocious rats, makes landfall. A life-and-death struggle ensues as the men seek to save themselves from the hungry horde, who swarm over the lighthouse. The three men barely survive fending off the rats when they break into the tower. The men escape into the lighthouse gallery, which has a metal trapdoor that the rats cannot gnaw through, and are able to use the light to signal an investigating patrol boat. Eventually the rats are lured off the island onto a barge loaded with meat, which is then set on fire by incendiary shells. Many of the rats die and the survivors are devoured by the sharks that infest the waters. The fates of the men are then revealed by the narrator: Le Gleo went insane from the events and was locked away in a French asylum, and Itchoua dies of infection from rat bites and scratches. The narrator continues to work in the lighthouse until his service time is over. ==Publishing history==