Evil Holds the Key — Norman Russell

Lucy Forster's marriage to wealthy young landowner Robert Davenant makes her mistress of Lowthorpe Hall, a gracious country seat in a remote Warwickshire valley. But she soon learns that Lowthorpe harbors a sinister and dangerous secret. Fearful rumors circulate, including the belief that something tangibly evil lurks in a sealed-off grotto beneath the house. Then Silas Markham, the Davenant's clever but devious librarian, is shot dead. And soon afterwards, Lucy makes an appalling discovery that threatens the family with total ruin. Arson and civil riot threaten the peace as Inspector Jackson and Sergeant Bottomley take on the case. As they struggle to restore order and solve Markham's murder, the horrifying truth of the Lowthorpe grotto must finally come to light.