Viola Doyle, who rides about town on her bicycle, a feat her mother thinks unbecoming to a young lady, loses a precious jewel when she collides with a young professor’s assistant. Mikhail, the young man she plowed into, returns the jewel and offers to help Viola and her grandmother research the mysterious gem’s origins. Together they learn that the gem is more than simple jewelry and is instead a powerful stone entrusted to a long line of protectors. But its keepers aren’t the only ones interested in the stone.