All of Alvirah's deductive powers and Willy's world-class common sense are called upon as the two stumble into a Christmas mystery. A woman abandons her newborn at a Manhattan church. Simultaneously, a thief is absconding with a treasured artifact, a chalice adorned with a star-shaped diamond. To elude police, he grabs the stroller and disappears. Seven years later, the mother returns to the scene and finds Alvirah and Willy helping neighborhood kids prepare for a Christmas pageant at an after-school shelter. Soon the savvy sleuths set out to solve the puzzle of the missing child and chalice -- and to unmask scam artists threatening to shut down the shelter.