The collection mainly focuses on The Secret Sharer, the story of a young ship captain who secretly shelters a fugitive sailor named Leggatt on board his ship. Instead of handing him over, the captain chooses to protect him in secret.
As time passes, the captain feels a strong psychological connection with Leggatt, seeing him as a kind of “double” or reflection of himself. This relationship forces him to question his sense of duty, morality, and authority.
In the end, the captain risks his ship and career to help Leggatt escape safely to shore.
The other stories in the collection also explore similar themes such as isolation, guilt, moral conflict, and human psychology.