The Hampstead Mystery

"Hallo! Is that Hampstead Police Station?"
"Yes. Who are you?"
"Detective-Inspector Chippenfield of Scotland Yard. Tell Inspector Seldon
I want him, and be quick about it."
"Yes, sir. Hang on, sir. I'll put you through to him at once."
Detective-Inspector Chippenfield, of Scotland Yard, waited with the receiver held to his ear. While he waited he scrutinised keenly a sheet of paper which lay on the desk in front of him. It was a flimsy, faintly-ruled sheet from a cheap writing-pad, blotted and soiled, and covered with sprawling letters which had been roughly printed at irregular intervals as though to hide the identity of the writer. But the letters formed words, and the words read:
SIR HORACE FEWBANKS WAS MURDERED LAST NIGHT
WHO DID IT I DONT KNOW SO IT IS NO USE TRYING TO FIND OUT WHO I AM YOU WILL FIND HIS DEAD BODY IN THE LIBRARY AT RIVERSBROOK
HE WAS SHOT THOUGH THE HEART