Murphy escapes a grueling life as part of a dogsled team, mercilessly driven so that their cruel owner can reach Nome before the Bering Sea thaws and word gets out to the mainland that gold has been discovered. When the first ships arrive, Murphy is taken in by two recent arrivals: Sally and her mother, who hope to make their fortune providing secretarial labor, so that they can buy their own stake, free from their wealthy but oppressive family back home in Seattle.
Life in the mining town is not easy for anyone. Murphy, Sally, and Mama live in a canvas tent on the beach with the thousands of other arrivals, all of whom are hoping to get rich. Mama uses her writing and typing skills and finds a day job in the recorder's office; at night, she types letters for the homesick prospectors. With Murphy always by her side, Sally helps her mother by addressing and delivering the letters to the post office and earns extra money sorting mail. She watches the miners on the beach as they use rockers, conveyor belts, and toms to hunt for gold, and she listens to their dreams and theories about how the gold got into the sand and how to retrieve it. Murphy repays Sally and Mama's kindness by serving as bodyguard in the rough frontier town. He saves his new family from robbers, who prey on the beach dwellers.
Unbeknownst to her mother, Sally uses some of her earnings to pay for equipment so she can set out to find her own "claim" before fall brings cold weather. She and Murphy head up the Snake River where she is sure they will find gold. They do, enough nuggets to buy Mama a real home, but they also encounter a blizzard…and Murphy's original owner, who has been looking for his valuable dog.