The present Earl of Northernly and his wife are waiting for Christmas and their new baby. But then the previous Earl's wife returns with a child who may be the real heir. Can Cousin Sarah and William be in time to unravel this mystery?

Christmas time should be joyous for Kit Aldean, the new Earl of Northernly, and his wife, Emily. They will have a new child arriving for the new year. But to their surprise, they first get a Yuletide visitor — the previous Earl's wife, who had vanished years ago. She presents them with a child who may be the real heir. Fortunately, their next visitors are Cousin Sarah and her husband, William. They've solved mysteries before, but can they manage this one in time?