The plot of the novel involves piracy in the South Atlantic during the mid-19th century, with a theme of survival in extreme circumstances, and events centering on an isolated lighthouse.

Verne was inspired by the real lighthouse at the Isla de los Estados, Argentina, near Tierra del Fuego and Cape Horn.

[2] Unbeknownst to Vasquez, Moriz, and Felipe, the chief lighthouse keeper and his helpers, the island was the domain of a dozen marooned pirates, who bide their time in wrecking.

Vasquez, the only survivor, spends several months until the dispatch boat Santa-Fé is due to return, surviving off the pirates' hidden stores of food in a cave.

Kongre, the band's leader, orders Carcante and the carpenter to climb the side of the lighthouse and murder Vasquez and Davis at the top, but they are shot as soon as their heads peek over the banister.