It's a distraction--and it helps.

I really must congratulate you, my dear M.Formery, on the admirable manner in which you have conducted this inquiry." M.Formery bowed, and regarded him with a touch of suspicion.
"There are one or two minor points on which we do not agree, but on the whole your method has been admirable," said Guerchard.
"Well, about Victoire," said M.Formery.

"You're quite sure that an examination, a more thorough examination, of her room, is unnecessary ?" "Yes, I think so," said Guerchard.

"I have just looked at it myself." The door opened, and in came Bonavent, one of the detectives who had come earlier from the Prefecture.

In his hand he carried a scrap of cloth.
He saluted Guerchard, and said to M.Formery, "I have just found this scrap of cloth on the edge of the well at the bottom of the garden.