Legends whisper of Dzamm, a fabled African city said to guard immense wealth. Captain Rawlins Ralph Dunn dispatches two ruthless henchmen to trace a path to this hidden metropolis, hoping to plunder its riches. Along the way, their greed turns deadly as they murder several Dzamm natives, and their expedition ends in a brutal reversal when a large pride of lions overpowers them and devours the intruders.
Nearby, Jungle Jim Johnny Weissmüller meets Li Wanna Elena Verdugo, the daughter of Dzamm's chief religious official Zoron. Li Wanna pleads for Jim's aid in fending off Rawlins and his mercenaries, who are bent on seizing the city’s rumored treasures. The rumor proves true: crates of precious stones lie hidden within the temple of Dzamm. After learning of the murdered natives, Jungle Jim and Li Wanna hurry toward the scene, only to find the henchmen's corpses. Faced with a threatening pride of lions, the agile adventurer and Li Wanna climb a tree to safety, and an African elephant arrives to scatter the cats.
Back at Zoron's residence, the pair discuss a peaceful solution: they decide to offer Rawlins a handful of diamonds in exchange for ending the raid. Meanwhile Li Wanna's brother Chot [Paul Marion] is hypnotized by Calhoun [Joseph Vitale], a calculating businessman, whose niece Norina [Myrna Dell] is also on Rawlins's payroll. Jungle Jim befriends a gorilla after rescuing it and its offspring from a ferocious lion, naming the creature Zimba [Ray Corrigan]. He then blocks Calhoun from learning the exact trail to Dzamm but is captured by Rawlins's followers. Norina, torn between loyalty and sympathy, attempts to free him but is killed by Calhoun.
Caw Caw, Jim's loyal bird, unties his ropes and helps him break free, allowing him to overpower several of the attackers. With Li Wanna captured, Jungle Jim reveals the path to Dzamm to Rawlins. They reach the temple, where the looting of priceless relics begins; Zimba and his gorilla clan attack the raiders, decisively turning the tide. Rawlins and his ally Wilson [George J. Lewis] manage a brief escape with Jungle Jim captive, but Zimba’s counterattack ends their raid for good. Chot, mortally wounded, asks for forgiveness before he dies. With the looters defeated and order restored, Dzamm begins to heal, and Jungle Jim’s courage helps safeguard the city’s legendary treasures.
