Joseph Conrad 
The secret sharer 

The story takes place at sea, near the Gulf of Siam, and is told from the perspective of a young nameless Captain. He is unfamiliar with the  ship, having only joined the company a fortnight earlier. A disturbing secret from the sea stirs the becalmed mood that numbs the crew. And it initiates a series of ruses by which the young captain, in his first command, undertakes to conceal the presence on the ship of the fugitive Leggatt, a projection of his anxieties and guilt. In Conrad’s most intense and evocative sea tale the exoticism of faraway places continues to represent one of the few escape routes from a positivistic world deprived of illusions. But this nocturnal and mysterious journey to salvation passes through the exploration of the darkness of the human soul.

Unabridged edition.