The Borgia Cabinet

When Detective-Sergeant Charlesworth of Scotland Yard was sent down to Aldersyke Manor to investigate the sudden mysterious death of Sir Charles Stanmore, he determined that, no matter what happened, if it proved to be a case of murder, he would find the culprit; for on this, his first big case, his whole future depended. Yet when he arrived on the scene there was very little on which to make a start.
Sir Charles, according to the doctor, had died from poisoning, though whether it was self-administered or not he was unable to say on his first examination. He hinted at murder. So Charlesworth set about solving one of the most amazing mysteries ever recorded in the annals of crime, thus adding another tremendous thriller to Mr. Fletcher's long list of successes.