The book's protagonist, Humphrey Van Weyden, is a literary critic who is a survivor of an ocean collision and who comes under the dominance of Wolf Larsen, the powerful and amoral sea captain who rescues him.

Its first printing of forty thousand copies was immediately sold out before publication on the strength of London's previous The Call of the Wild.

[1] Ambrose Bierce wrote, "The great thing—and it is among the greatest of things—is that tremendous creation, Wolf Larsen... the hewing out and setting up of such a figure is enough for a man to do in one lifetime...

"[2] The personal character of the novel's antagonist "Wolf" Larsen was attributed to a real sailor London had known, Captain Alex MacLean.

The MacLean Captains maintained their ties to Cape Breton Island despite having spent much of their lives sailing the Pacific Coast.

"[7] Nietzsche and Schopenhauer are mentioned in the second sentence of the novel as the preferred reading of the friend Humphrey Van Weyden visited before his shipwreck.

The Sea-Wolf tells the story of a soft, domesticated protagonist — an intellectual man named Humphrey Van Weyden — forced to become tough and self-reliant by exposure to cruelty and brutality.

The story starts with him aboard a San Francisco ferry, called Martinez, which collides with another ship in the fog and sinks.

Brutal and cynical, yet also highly intelligent and intellectual, he rules over his ship and terrorizes the crew with the aid of his exceptionally great physical strength.

Being interested in someone capable of intellectual disputes, he somewhat takes care of Van Weyden, whom he calls "Hump", while forcing him to become a cabin boy, do menial work, and learn to fight to protect himself from a brutal crew.

Searching for his assailant, he ventures into the sleeping quarters, located beneath the main deck, the only exit being a ladder.

Larsen however, demonstrating his inhuman endurance and strength, manages to fight his way through the crew, climb the ladder with several men hanging off him, and escape relatively unharmed.

During this section, the Ghost picks up another set of castaways, including a young unmarried woman named Maud Brewster.

Wolf kidnapped several of Death's crew and forced them into servitude to fill his own ranks, lost previously during a storm.

Larsen attempts to assault Brewster, but is stopped by one of his intense, immobilizing headaches, which allows her and Van Weyden to steal a boat and flee.

He feigns paralysis and attempts to murder Van Weyden when he draws within arm's reach but just then has a stroke that leaves him blind and the right side of his body paralyzed.

He grows stronger as the story progresses, physically through the manual labor, and spiritually as he endures the various hardships, including his tumultuous relationship with Wolf Larsen.

Upon meeting Maud Brewster, he realizes just how much he has changed, gaining muscle mass, a more rugged appearance, and a different outlook on life.

Though he is in effect the captain's prisoner, Larsen shows him favoritism and occasionally acts as a father figure, giving advice on how to survive aboard the ship.

Throughout the book, Larsen compliments Van Weyden on his growth, eventually telling him he is proud of him, and calling him a real man, able to stand on his own legs.

Physically, Larsen is described as approximately 5 feet 10 inches (1.78 m) in height, with a massive build: broad shoulders and a deep chest.

[8] He is extremely intelligent, having taught himself a variety of fields, including mathematics, literature, science, philosophy, and technology.

He routinely takes men hostage, castaways such as Van Weyden and seal hunters from other ships, and uses them to fill his own ranks when needed.