III
The doctor invited Lestrade for lunch, and after they finished they shared a bottle of beer in his lovely terrace, some fifty yards from the sea. Conversation drifted through different subjects, but White was eager to hear the inspector's explanation of the murder case of that very morning.
"I don't get it," he said, "Mary was the only one beyond suspicion."
"Only as long as you though the poison was in the water," replied Lestrade. "That's why she had to spill it on the carpet: because it was innocuous, there was nothing but water in the glass. Once this proved, she would have become the only suspect, for she was the only one who had the chance to give a dazed Michael a pill or something unnoticed, while you were getting the cushion from the wardrobe. He drank a gulp of water, alright, but only to swallow something… a pill. Plus, had the poison been in the water, Michael wouldn't have had enough time to put the glass back on the table, for his death was that quick. On the contrary, the pill had to disintegrate itself first.
"Another clue; the tablecloth of the night table was creased, as it had apparently been used to avoid leaving fingerprints on the glass. But you and Sally had already handed the glass, so it was not necessary for any of you to proceed like that. On the other hand, Mary had not touched it yet, and so she had to take the precaution of grabbing it with the tablecloth.
"Finally, I ordered one of the constables to fill this little flask with water, place it over the table and hide himself somewhere with a view to the kitchen… and the flask, of course. Then I told the other constable to go out slamming the front door hardly. Then, at last, I asked Mary to fetch the flask, making her believe that you had saved a sample of the water from the glass in it, and that the constables were out. Fortunately, you had gone to the kitchen to call the police before the water was spilt and she didn't call my bluff. The hidden constable saw her spill the flask's contents in the sink; and since Sally had gone to open the door at the moment of my arrival, Mary though that everyone was to be suspected for this new complication."
"How simple!" said the doctor as he lit his pipe.
THE END