Anna Katharine Green 
The step on the stair [EPUB ebook] 

‚The Step on the Stair‘ is a detective novel written by Anna Katharine Green, one of the first American writers of detective fiction. Published in 1923, the book follows detective Ebenezer Gryce as he investigates the mysterious death of wealthy businessman Mr. Adams, who is found dead in his mansion with no apparent cause of death. With a cast of suspicious characters, including the victim’s wife and business partner, Gryce must navigate the twists and turns of the case to uncover the truth.