The House on the Roof — Mignon G. Eberhart

In this “Class A mystery” from the golden age of detective fiction, a woman witnesses a murder in the penthouse of her building and becomes a suspect (The New York Times).

It's an invitation Deborah should never have accepted. Tea with Mme. Mary Monroe, the famous opera singer, in her eerie house on the roof of their apartment building. Once there, what can Deborah do but politely agree to accompany the lonely Madame on the piano? But just as the singer is swept up in the strains of Massenet's ‘Elégie,' a shot rings out and Madame crumples to the floor. From her seat at the piano, her back to the door, Deborah doesn't see a thing. Instead, she becomes the lead suspect in the hideous crime. An accusation that sends her back up to the top floor for answers, only to discover even greater terrors.

“A terrible tale -- very well done. Murders in an apartment house, and a successfully sustained atmosphere of horror. A-1 mystery.” -- Kirkus Reviews