After a new pipe organ is installed at a Boston church, an organist vanishes. An infant crawls in the dark, up the cold stone steps of Boston's Church of the Commonwealth. It is a miracle that Alan Starr notices the child, so focused is he on the church's new organ, whose pipes he is about to hear for the first time. He takes the baby in his arms and goes inside to inspect the magnificent new instrument, designed to the specifications of the church's master organist, mentor to Alan and to Rosalind, the baby's mother. When Alan takes the child to his neighboring home, he finds blood on the floor and no trace of Rosalind. In what should be the church's finest hour, tragedy has struck. With the help of Homer Kelly, Harvard professor and casual sleuth, Alan combs the city for the missing mother. Together they learn that even God's house can be a haven for the devil.