Somewhere Down the Line: The Legend of Boomer Jack is based on the true story of a dog who rode the lumber trains of Northern California in the early 1900s. Boomer Jack is a lovable railroad dog who has ridden the rails since he was a pup. Although he belongs to the mayor's wife, who wants him to be a house dog, Boomer can't resist the call of a train whistle. Boomer has many friends around the town of Willits, including a kind-hearted station master and a locomotive engineer and his trusty fireman, but no one could love him more than a ten-year-old girl named Sara Parsons. Saddened by the recent death of her father in a tragic train accident, Sara looks to Boomer to ease her loneliness. But she soon discovers that it's impossible to keep a railroad dog away from the trains for long. Though Boomer is content to spend his days chasing adventure on the rails, trouble arises for the town when Mayor Belmont, who is also president of the Northwestern Pacific Railroad, decides to route his trains around Willits to another town. Meanwhile, Boomer has problems of his own when he is wrongly accused of chasing livestock and Fisk, a boozing dog catcher, sets out to capture him. After a narrow escape from Fisk, Boomer joins engineer Paddy and fireman Jonsey on a high-speed locomotive ride to San Francisco. The trainmen and their canine companion visit the city and return home with a second dog, Lucky, who becomes Boomer's new love. Once back in town, troubles escalate for both Boomer and the town of Willits when an angry Fisk tries to take his revenge. In the end, it's up to Sara to save the day, and learn a most important lesson from Boomer: True happiness is not to possess, but simply to love.