The Crimson Cryptogram by Fergus Hume

"Have you finished locking the drawers, Janet? " asked Hilda, impatiently.

But Janet did not answer. In a tumult of emotion she was staring at the red pocket-book. There it lay in the drawer, carelessly thrust in with loose papers and old letters. No attempt had been made to hide it. No doubt the drawer was locked, and but for Hilda's freak would have been opened by no one but its owner. Schwartz had not thought it necessary to conceal the book more completely. At once it flashed into Janet's mind that the German had murdered Edgar, since no one but the murderer could have become possessed of the pocket-book. In the meantime Hilda, uneasy at Janet's silence, repeated the question.