Marlow parallels the Intended with Kurtz's African mistress. While the Intended has "fair hair," a "pale visage," and a "pure brow," and she is dressed simply in black, the stunning African mistress is "draped in striped and fringed cloths" and "bedecked with ... charms." Both women loved Kurtz. Marlow wants to protect the Intended, for women like her, civilized women, in his view "are out of touch with truth."
He cannot tell her Kurtz's last words were "The horror! The horror!" because "it would have been too dark--too dark altogether." Marlow recognizes the truth of his journey; he has shared the details with his friends on board the Nellie, apparently sparing nothing. Furthermore, he knows no good would be served by telling the Intended what Kurtz had become. She needs some memories to cherish as she mourns the man she loved, a man who changed drastically because he succumbed to the lure of ivory.