Ace Double G-539 (1965): containing Composition for Four Hands, bound with The House - both sides by Hilda Lawrence (pen-name of Hilda Kronemiller) - these are mysteries/gothics. Originally published as a collection of 2 novellas as Duet of Death - in 1949. (Note the subtitle or pre-title on each side of this book: "Duet in Death.") Original titles were: "Death Has Four Hands" and "The Bleeding House."