"The Secret Sharer" is Conrad at his best. It tells the story of a young man on his maiden voyage as captain in the British Merchant Service, isolated and endangered by his loyalty to a stowaway. Conrad had a special gift for writing about young men — especially young seamen — facing a life-altering challenge. The novel "Lord Jim" is about a similar challenge, which the young seaman fails to meet, thus dooming himself in a very subtle area of his ego. Conrad's novella (half-way between a "short" story like "Sharer" and a novel) "The Shadow Line" also involves a nerve-wracking challenge to a young sea captain. Actually, the great novella "Typhoon" involves a challenge too, but to a much older sea captain.
At the time that Conrad decided to write "Sharer," he was working on a long, tense novel about Russia ("Under Western Eyes") that had nothing to do with the sea. It's a very fine novel, but Conrad suffered so much in scratching it out that the experience might have shortened his life. By contrast, he wrote "Sharer" with the greatest of ease, and it's almost perfect. Conrad had been a Merchant Service captain himself (which is how he happened to add English to his native Polish and near-native French), and it may be that he was more comfortable when the conflict was in his element, aboard ship.
At any rate, the "The Secret Sharer" raises questions that critics still don't agree on. One of them is simply whether the young captain is only imagining his secret guest. You be the judge, but I think there's a clear answer to that question. Above anything else, the story is exciting. It's long for a short story — almost a novella — but you might well find yourself reading it all in one sitting. If you like intelligent, vivid suspense, you're bound to enjoy this experience. The story can be read again and again, revealing new perfections each time.