Crossword Mystery by E. R. Punshon

Young detective-constable Bobby Owen believed that he had received a very nice assignment. Mr. George Winterton, a retired stockbroker, believed that someone was going to kill him. His twin brother Archibald, had recently drowned during his morning swim, and George believed that he had been murdered although there was no evidence that this was the case. Bobby Owen was assigned to spend a month or six weeks with Mr. Winterton to determine if someone was really trying to kill him. Bobby was to pretend to be a young protege of Mr. Winterton, and never to admit that he was a policeman.

Upon his arrival, Bobby met the occupants of Mr. Winterton's house on Snuffby Cove. There was his nephew Colin Ross who had a fondness for gambling on horse racing.  Winterton had another nephew Miles who was not presently staying there. There were Mr. and Mrs. Cooper who cared for the house and the grounds. Mrs. Cooper appeared to be a very intelligent woman who managed both the house and George Winterton. Her husband did not seem to be very clever. There was also Miss Raby who was George's secretary. George Winterton was writing a book on maintaining the gold standard. He and Miss Raby were quite keen on crossword puzzles - both in solving and writing them.

Bobby became acquainted with the neighborhood and with Winterton. It seemed that someone had come up with money making plan to convert some of the area into a summer recreation site. Both Archibald and George were opposed to the idea, but this seemed to be the only motive that Bobby could find for killing them. Then one night, Bobby became very worried about George Winterton's safety. He made sure that Winterton locked his bedroom door and window. Bobby was so worried that he slept in the hall way outside of Winterton's door. The next morning, George Winterton was found dead outside on the lawn underneath his bedroom window. It seemed like a locked room, but it proved to be easy to explain.

Then Bobby took a serious look at the crossword puzzle which George Winterton had been writing. The puzzle and the clues are included in the book in case the reader wants to try his hand at it. Bobby found that the solution of the puzzle proved a great help in providing the solution to the reason for the murders and from the reason, he deduced the identity of the murderer of both George and Archibald Winterton.

This book was published in 1934 and is the third in the series of 35 novels in the Bobby Owen series.