In the Heart of Darkness Why does Marlow try to capture Kurtz alone?

Marlow tries to capture Kurtz alone because he believes that Kurtz's madness and power over the natives will make it difficult for a group to apprehend him successfully. Marlow also sees it as a personal challenge to confront Kurtz alone and test his own strength and resolve. Additionally, Marlow wants to witness personally the extent of Kurtz's darkness and confront him one-on-one.