The monster of Grammont

The Monster of Grammont is a 1927 mystery thriller novel by the British writer George Goodchild, a prolific author of thrillers in the style of Edgar Wallace and Sydney Horler. It uses the elements of the traditional country house mystery, with the setting shifted to Continental Europe in the interwar years. This was one of the most popular of his numerous writings, released by Hodder and Stoughton. It was published in America by The Mystery League in 1931. (This summary is from Wikipedia.)