Korak is attacked by Chief Buto who tells him that Tarzan has killed his son, Kumo. Korak defeats him, and they decide it must be an impostor who has done the deed. They see from the tracks that Kumo is not dead but a prisoner. They find the false Tarzan & Kumo being forced to load ivory tusks onto a small steam launch and follow it by night in a canoe. The Arab ivory traders head toward a dhow as a storm rises. In the morning they find the launch deserted and broken on the rocks with only Kumo aboard. All were killed but the impostor Tarzan. They are on a small island in the Mozambique channel where they come upon a deserted Portuguese town. The false Tarzan tries to kill them with a stone block from an old church belfry, then accosted by Korak, he falls to his death. They salvage the steam launch and sail home -- fast friends.