"I thought there might be a spark there still, but I was mistaken," he went on. "He looked so natural—and Mrs. Langmore looked natural, too, for the matter of that. But both were stone dead."
"What was the cause of death?"
"That is something of a mystery. I have tried my best to get at the bottom of it, but I cannot, nor can my colleague, Doctor Soper."
"Were the pair strangled, smothered, poisoned?" suggested the coroner.
"I have a theory that they were poisoned, but not in an ordinary way. Neither Doctor Soper nor myself could find any traces of ordinary poison."
"What is your theory?"
"Something was used to stupefy them, and so much was used that it killed them."
"In that case the murder might have been unintentional?"
"Yes. Somebody might have thought to stupefy Mr. Langmore and then rob him. But the drug, being too powerful, or used too long, might have done its deadly work. Then the crime may have been discovered by Mrs. Langmore and the murderer might have turned on her to conceal his first wrongdoing."
"Hum. Have you—ahem! any idea of the nature of the poison?"