1846, nineteen-year-old pioneer Sarah Whitlock is trapped in a Rocky Mountain blizzard—her father dying of gangrene, her siblings starving. Chasing a rat across ice, she falls into a crevasse and wakes up behind a modern Costco. Mistaken for a costumed employee, she starts smuggling rotisserie chickens, vitamins, and antibiotics back through time to save her family—while accidentally becoming America's most viral TikTok star. But her wagon train is turning against her, and one door won't stay secret forever.