The Earth has been conquered by an alien race known as the Illumidus. Captain Harlock refuses to allow his ship, the Deathshadow, to be used by the Illumidus and deliberately crashes it - rendering it inoperable. After meeting the genius mechanic Toshiro, the free space trader Emeraldas and witnessing the destruction of a planet previously conquered by the Illumidus, Harlock becomes a space pirate and is exiled from Earth along with those who chose to follow him.