Although Heart of Darkness deals with profoundly dark themes, sex is not one of them. This is because the vast majority of the characters are men that travel into the core of Africa with no women aboard the ship. That makes sex difficult for the average nineteenth century heterosexual male. The closest anyone comes to saying anything even vaguely sexual is Marlow’s description of the warrior woman as "wild and gorgeous." We realize that this woman is Kurtz’s mistress, but there are no steamy scenes. It is obvious that Marlow considers both the warrior woman and Kurtz’s Intended (fiancée) to be beautiful, but he shows no further desire for either of them.
Readers may even question the presence of women within the novel. The two main female characters – the warrior woman and the Intended – are both nameless (not that that’s uncommon in this novel) and described in rather ghostly terms. They do not seem as human as Marlow or even the nameless male characters. The warrior woman is described as "an apparition of a woman" while the Intended is seen only through light imagery. The few other women mentioned – the two knitting women, Marlow’s aunt, and the woman in the painting – either have a supernatural quality to them or are never actually seen in person within the text.
Thus, one could argue that women are utterly absent from the story, though their influence is not. Why is this? If Marlow is at all representative of Conrad’s beliefs, his comment that "we [meaning men] must help them [meaning women] to stay in that beautiful world of their own, lest ours gets worse" becomes particularly relevant. If Marlow cuts women out of his tale to preserve the beauty of these particular characters, Conrad cuts women out of Heart of Darkness to preserve their separateness from this rather depressing and gloomy world.