Returning from RAF service after World War II, Group Captain John Clayton, Tarzan of the Apes, discovers that his home jungle has been invaded by a military force-from Mars! Determined that a hostile Martian colony not take root in Africa, Tarzan knows that he must return to the dying red planet to seek the help of his former ally and fellow Earthman, John Carter of Virginia, Warlord of Mars. Recruiting Barsoom's greatest fighters, together they launch an expedition to locate the hidden base. Their only clue: the cryptic word Nulthoom. And they must locate it before a second space-faring ship is sent to Earth-or else Africa will be flooded by Martian colonizers!