Hanaud looked about him.
"Yes," he said. "This room stood open for a week after Madame's funeral. It would have been a miracle if we discovered anything which could help us."
He went to the bed, which stood with its head against the wall midway between the door and the windows. A small flat stand with a button of enamel lay upon the round table by the bed-side, and from the stand a cord ran down by the table leg and disappeared under the carpet.
"This is the bell into what was the maid's bedroom, I suppose," he said, turning towards Betty.
"Yes."
Hanaud stooped and minutely examined the cord. But there was no sign that it had ever been tampered with. He stood up again.
"Mademoiselle, will you take Monsieur Girardot into Jeanne Baudin's bedroom and close the door. I shall press this button, and you will know whether the bell rings whilst we here shall be able to assure ourselves whether sounds made in one of the rooms would be heard in the other."
"Certainly."
Betty took the Commissary of Police away, and a few seconds later those in Mrs. Harlowe's room heard a door close in the corridor.
"Will you shut our door now, if you please?" Hanaud requested.