During the long, hot spring of 1910 it seemed all 12-year-old Jo Harper could do was wait. Wait for her father, wait for her friends, wait for the comet that might appear in the sky and wipe out the whole town of Willowby, Wyoming, once and for all. But when Wild West legend Abby Drake arrives in town lugging an orphaned baby calf, an old-fashioned revolver, and a mystery shrouded with superstition, it's up to Jo to take action. Why is Abby in town? Who is she after?