The Sea-Wolf features a character named Humphrey van Weydon, nicknamed "Sissy" for his lack of masculinity. A gentleman and occasional literary critic with a substantial inheritance, van Weydon starts the story aboard a ferry, living a calm, boring upper-class life. "Then everything happened, and with inconceivable rapidity": his ship is destroyed and he is cast adrift before blacking out in the cold water.
When he awakens, he is aboard a sealing vessel named Ghost. Within moments, he witnesses the callous removal of the dead first mate, who is unceremoniously cast into the sea (London himself witnessed a similar burial at sea aboard the Sophia Sutherland). Another crew member is promoted in his place, leaving room for "Hump," as the protagonist is now renamed — though his membership in the crew is not voluntary. The captain, described as a gorilla or tiger (or later, "devil"), is Wolf Larsen, a powerhouse of a man who takes Hump under his wing. Throughout the book, the two debate "immortality" versus "materialism"; the human soul versus animalistic survival instincts; the nature of manhood and masculinity. According to the captain:
"I believe that life is a mess... It is like yeast, a ferment, a thing that moves and may move for a minute, an hour, a year, or a hundred years, but that in the end will cease to move. The big eat the little that they may continue to move, the strong eat the weak that they may retain their strength. The lucky eat the most and move the longest, that is all."
Wolf Larsen is, without doubt, one of the most horrifically compelling characters in American literature. He is manipulative, cruel, intense, and unstoppable. Soon enough, Hump sees his old "sissy" nature being replaced by one closer to Wolf Larsen's image, at the same time gaining power and influence (as well as animosity) aboard the Ghost. Both allies and enemies, the tension between the two never ends and the reader of The Sea-Wolf is in constant fear that one will kill the other. Contemporary Gilded Age readers were shocked by the violence, cruelty, and nihilistic philosophical debate; readers today might feel equally shocked and equally enthralled. As Hump describes to a newcomer aboard the Ghost:
"You must understand... and understand clearly, that this man is a monster. He is without conscience. Nothing is sacred to him, nothing is too terrible for him to do. It was due to his whim that I was detained aboard in the first place. It is due to his whim that I am still alive. I do nothing, can do nothing, because I am a slave to this monster."