One year after the events of the original film, this sequel uses a frame tale to present three self-contained episodes via flashback. Jane Porter, Olivia d'Abo, and Tarzan, Michael T. Weiss, celebrate their first wedding anniversary with the help of two loyal companions: the elephant Tantor, Jim Cummings, and the gorilla Terk, April Winchell.
In the first episode, the trio recalls the time when Jane’s friends arrived to rescue her, mistakenly believing she was held captive in the jungle. After learning the truth, they decide to stay for a visit. Jane organizes an English-style picnic for her guests, but Tarzan declines, worried that Jane might be embarrassed by his savage habits. The picnic is interrupted when two panthers, Nuru and Sheeta, attack Jane and her friends, forcing them to flee into the deeper regions of the jungle. As Jane teaches her friends survival techniques, they are ambushed again, this time only Tarzan can pull them to safety. When Jane and her friends depart the next day, they thank her for the adventure and say they hope to visit again soon.
Back in the present, Jane contemplates expensive gifts, particularly jewelry, prompting Terk to remind her of the time Tarzan tried to surprise her with a diamond. Tarzan had led two men, Johannes Niels, John O'Hurley, and Merkus, Jim Cummings, to a volcano that housed a diamond mine, planning to obtain one diamond to present to Jane, with the two men delivering it to him in return. But inside the volcano the trio are betrayed, and the others turn on Tarzan in their bid to claim all the diamonds for themselves. The volcano erupts, trapping Tarzan, Jane, and Professor Porter within, yet they manage to escape before lava closes in. Tarzan later rescues Johannes and Merkus, though their diamonds are lost in the process. Johannes and Merkus are then arrested and taken back to England.
Professor Porter chimes in, suggesting that Jane and Tarzan celebrate their anniversary with a dance. This leads Terk to reminisce about a past visit from Jane’s old friend Robert Canler, whose appearance had once strained Tarzan’s trust due to jealousy and fear. The memory culminates when Canler reveals himself as a double agent for the Germans during World War I, having come for a code machine hidden inside a music box Jane kept safe. Canler abducts Jane, but Tarzan tracks him down with the help of Nigel Taylor, an RAF pilot who had been on Canler’s trail. Taylor takes Canler into custody, flying him back to England to stand trial. Jane is saddened that Tarzan was right about Canler, though Tarzan senses there may still be some good in him, given that he returned to save Jane at one point.
Having exhausted ideas about anniversaries fitting Tarzan’s uncivilized life, Jane returns to the treehouse in disappointment—only to discover a long-awaited surprise. The party had been planned all along by Terk, Tantor, and Professor Porter, who kept everyone distracted while Tarzan’s group prepared the decorations. Tarzan, wearing his father’s suit, presents Jane with a diamond ring crafted from the same diamonds found in the volcano, a token of their enduring bond. The celebration kicks off with a dance, and the film closes with Tarzan and Jane dancing under the moonlight, surrounded by fireflies as everyone rejoices.
