Carolyn Wells 
Raspberry Jam 

Raspberry Jam is a classic locked-room whodunit featuring Detective Fleming Stone and is widely considered to be one of the best of the Fleming Stone Mysteries. Millionaire Sanford Embury is found dead in bed, alone, with the door of his second-story bedroom bolted shut from the inside. He was known to be a controlling husband, refusing to give his pretty young wife an allowance of cash or her own checking account. Was his wife a party to the murder, or perhaps did she commit the murder in a fit of rage? Who else had a motive? And how does a clue of raspberry jam point to the killer? (goodreads)