A spy, Albert Werper, has been sent by Tarzan's long time foe, Achmet Zek, to abduct Jane. His plan changes when he discovers that Tarzan is bankrupt and must return to the lost city of Opar to bring back more gold. While Tarzan and the spy are in the treasure tomb, an earthquake strikes Tarzan down and blocks the exit. The only way out leads Werper to the sacrificial chamber of the Flaming God, where he soon finds himself the next victim. Tarzan is quick to recover his strength - but not his memory!