"The Secret Sharer"
When Conrad first published this story, he called it "The Secret-Sharer." It was only later that he removed the hyphen. You can see how this tiny little piece of punctuation would change the meaning of the story, because with the hyphen left in, the story sounds like it's about a person who shares a secret. When you leave the hyphen out, though, it opens up the possibility that Leggatt is himself a "secret" person who shares things with the captain.
This version without the hyphen definitely serves Conrad's purpose better, because it's clear that Leggatt and the captain share a lot more than just secrets. They share clothes, for example, as well as personal experiences and their deepest emotions. So next time someone smack talks about how hyphens don't matter, just point them in Conrad's direction.