A Christmas Odyssey by Anne Perry

A Christmas Odyssey: A Novel - Henry Rathbone’s friend’s son, Lucien has disappeared into London’s underground.  Henry knows that Hester Monk has connections to the underground at her medical clinic.  There, Henry meets Squeaky Robinson, Hester’s administrator.  They meet up with Crow, a doctor to the unfortunate.  Together, Henry, Squeaky, and Crow search the worst of London’s underground to find Lucien.