 A now amnesiac Tarzan and Werper escape from Opar, bearing away the sacrificial knife of Opar which La and some retainers set out to recover.There is intrigue and counter intrigue the rest of the way.Burroughs' novel served as a partial basis (along with "The Return of Tarzan") of the silent film serial "The Adventures of Tarzan" (1921); subsequently it was the basis for the silent film "Tarzan the Tiger" (1929).