The Thorndyke series stretched from the Edwardian era to the Golden Age of Detective Fiction It was published in the United States the same year by Dodd, Mead under the alternative title The Unconscious Witness.

Tom Pedley an experienced painter is near Hendon painting a seemingly rural scene in woodland about to be developed for housing as part of London's growing suburbs.

He unknowingly becomes witness to a murder when he observes three strange figures in the woods shortly before one of them is found dead.

At the same time, Pedley's attractive but pushy neighbour Lotta Schiller, an aspiring painter of modern art, intrudes on his bachelor existence.

Some clues seem suggest that she has been murdered but Scotland Yard again find the trail running cold.