Kathy O'Fallon arrives from Boston to her uncle John's cabin near the Canadian border and meets Sgt. Mike Flannigan of the Canadian North West Mounted Police. They marry in the middle of winter, and he takes her, by dogsled, to the remote northwest village of Hendricks Hole, where his duties include emergency tooth extractions, vaccinating Indians from smallpox, and setting the broken legs of sled dogs. Kathy soon becomes pregnant, and after the baby of her best friend, Mrs. Howard, is born dead, she insists Mike transfer to a larger settlement for the birth. When Kathy is in her third trimester, they travel by canoe to Fort Manette, and she is forced to wait in a remote cabin with its owner, the stern Mrs. Mathers, while Mike fetches a doctor. After a day of delirium, Kathy wakes to find that she has given birth to a girl with the help of a kind midwife named Sarah Carpentier, who becomes Kathy's best friend at the fort. One day, Sarah's son Pierre's arm is crushed by a boulder, and has to be amputated. Sarah is greatly disturbed by the tragedy, but her friend, Georgette Beauclaire, is grateful that the boy is alive and tells Kathy that her own daughters, Madeleine and Barbette, are her third family. When a woman lives in such remote regions, Georgette explains, she expects to rebuild her family over and over again after the inevitable death of loved ones. Kathy, Mike and little Mary live happily until, at age eighteen months, Mary dies from diphtheria during an epidemic. Kathy, unable to handle the brutalities of life in an isolated settlement, leaves Mike to return to Boston. However, when Mike sadly returns to his and Kathy's first home in Hendricks Hole, he finds Kathy waiting for him. After seeing Mrs. Howard's new healthy baby girl, Kathy says, she decided it was time to start a new family with Mike.