Episodes in the novelist's life: In 1890, young Jack London quits a cannery job to try oyster piracy. Later, he signs on for a sealing voyage, tries Yukon prospecting and a brief university career, loving and leaving women along the way. Instead of riches, he gets story ideas. Suddenly, he finds success and a delectable lady; but the urge to adventure won't let him go.

In Oakland, California, in 1890, Jack London, who dreams of becoming a writer, quits his cannery job after a female employee's hands are crushed in a machinery accident. Mammy Jenny, Jack's maid and surrogate mother, lends him her savings so that he can buy a boat and earn his living hauling oysters from the San Francisco Bay. After he buys the boat from French Frank, who gets a cut of all his business, Jack discovers oyster pirate Mamie stowed aboard, and agrees to a partnership with her. They are later joined by a third partner, Scratch Nelson. Early one morning, the boat pulls into dock after a night's work of stealing from other traps and is fired at from the dock by the police. Scratch is killed, and although Mamie has fallen in love with him, Jack decides that oyster piracy is too dangerous a business and quits. Later, Jack signs on as an able-bodied seaman for a seven-month sealing trip. When his shipmates tease him about his reading habits, weathered sailor Old Tom comes to his defense, and the two become fast friends. One day Jack turns the tables on Red John, a rough practical joker who has harrassed him since his first day aboard ship, and proves his manhood once and for all in a fistfight with the sailor. That night, Jack writes about the sailor, calling him "the sea wolf," and is encouraged in his literary efforts by Old Tom. After his ocean adventures, self-educated Jack enrolls at the University of California at Berkeley. When a teacher selects one of his stories as an example of an overactive imagination, Jack defends his work, stating that having witnessed the vagaries of life, he only writes about cruelty with the hope of alleviating it. Realizing that formal training will not give him the education he craves, Jack leaves school and goes to Dawson City, Alaska, intending to capitalize on the gold strikes in the Yukon. One night in a saloon, Jack meets Greek singer Freda Maloof, and is delighted by her knowledge of Lord Byron's poetry. Although Freda falls in love with Jack, he leaves as soon as news spreads of a major gold strike eighty miles away, determined to earn enough money so that he can spend his time writing instead of working. Eventually Jack ensconces himself in a remote cabin in the wilderness with his German shepherd, Buck, and writes a novel about the dog titled Call of the Wild . Publisher George Brett pays Jack for his manuscript, and when Jack meets his secretary, Charmian Kittredge, he learns that she has already become smitten with him through his writing. Jack soon falls in love with Charmian, and on New Year's Eve, a newspaper publisher asks Jack to cover the Boer War for him. In keeping with her promise that she will never entrap Jack, Charmian encourages him to go. Jack returns, older and wiser, bearing many gifts for Charmian, who still wants to marry him. The next day Maxwell sends Jack to cover the burgeoning war between Japan and Russia, and Charmian again agrees to wait for him. Jack is one of many correspondents in Japan, most of whom believe that Russia will soon make peace with Japan. Jack, however, is suspicious of Japanese intentions, knowing that they are sending troops into Korea. When the Japanese refuse to allow correspondents to travel into Korea, Jack makes a bet with reporter Dick Davis, who is sure that Jack cannot cross the Korean border. Jack disguises himself as a Chinese worker, and gets passage on a "sampan" which crosses the Yellow Sea. Once there, he witnesses Japan's invasion of Korea firsthand. In Korea, Jack is befriended by Oxford-educated Captain Tanaka, who treats him as a guest and outlines for him Japan's plot to take over all of Asia, and ultimately, the world. Jack scoops all of the other papers and sends his report about the Japanese invasion of Korea. After some time, Jack is arrested as a Russian spy, and is thrown into prison with the Russian prisoners. Jack is horrified by the brutal treatment of the prisoners, who are denied water. When the dehydrated prisoners break free of their cell to slake their thirst at a well, the Japanese guards laugh as they gun them down. Davis learns of Jack's arrest and alerts the American government in Washington, D.C. President Theodore Roosevelt demands from the Japanese government Jack's immediate release, but upon his return home, he finds that no one believes his story of the Japanese plan to overtake the world, and is disappointed when Maxwell refuses to print his articles. As Jack and Charmian leave the publisher's office, Charmian reaffirms her love for Jack, and celebrates him for his courage and honesty.