The Doom from Planet 4 ♦ By Jack Williamson

A Ray of Fire, Green, Mysterious, Stabs Through the Night to Dan on His Ship. It Leads Him to an Island of Unearthly Peril.
Dan McNally's tranquil night aboard his schooner in the tropic is suddenly torn asunder when he receives an SOS from a nearby island. Soon after a ray of green light darts out from the island and destroys his ship. After swimming ashore and fighting a mechanical monster he befriends a beautiful girl. After she unfolds her dramatic story, he realize that he has to destroy the mysterious base on the island or the whole planet Earth will be destroyed by the inhabitants of Mars, which is the Doom from Planet 4!