The one where the hero fights a crocodile, the damsel takes over the ship at gunpoint, and the cook dies a hero:
Tarzan’s infant son, Jack, is kidnapped by his nemesis, Rokoff the Russian. Rokoff’s plan is to take Jack to the primordial vastnesses of Darkest Africa and give him to the cannibal tribes–not to kill, but to raise as their own in his own twisted evolutionary programme for the Greystoke family. The father an ape–the son a cannibal. Rokoff does even better than he thought he would, because with baby Jack as bait, he manages to capture both Tarzan and Jane (separately). Tarzan he maroons on an uninhabited island, Jane he keeps–for himself.
But the uninhabited island is home to a tribe of Mangani, of whom Tarzan soon becomes leader and escapes to the mainland; Jane gains the sympathy and help of the cook, and escapes to the mainland, and a variety of twists and turns (and crocodiles) keep them from actually finding each other until the very last chapter. (Burroughs was an expert at maddeningly delaying reader gratification with headlong coincidences, random twists, and sudden crocodiles.)
Will Tarzan go down beneath the clubs and spears of the frenzied cannibal horde? Will he live to save his child and his wife? Will Jane escape the clutches of Rokoff and reach safety with her baby? Will Rokoff live to twirl his moustache another day?
You already know the answer…