“Yes,” said Ricardo.  “Helene Vauquier made a slip there.  She should have given her a false name.”

Hanaud nodded.

“It is the one slip she made in the whole of the business.  Nor did she recover herself very cleverly.  For when the Commissaire pounced upon the name, she at once modified her words.  She only thought now that the name was Adele, or something like it.  But when I went on to suggest that the name in any case would be a false one, at once she went back upon her modifications.  And now she was sure that Adele was the name used.  I remembered her hesitation when I read Marthe Gobin’s letter.  They helped to confirm me in my theory that she was in the plot; and they made me very sure that it was an Adele for whom we had to look.  So far well.  But other statements in the letter puzzled me.  For instance, ’She ran lightly and quickly across the pavement into the house, as though she were afraid to be seen.’  Those were the words, and the woman was obviously honest.  What became of my theory then?  The girl was free to run, free to stoop and pick up the train of her gown in her hand, free to shout for help in the open street if she wanted help.  No; that I could not explain until that afternoon, when I saw Mlle. Celie’s terror-stricken eyes fixed upon that flask, as Lemerre poured a little out and burnt a hole in the sack.  Then I understood well enough.  The fear of vitriol!” Hanaud gave an uneasy shudder.  “And it is enough to make any one afraid!  That I can tell you.  No wonder she lay still as a mouse upon the sofa in the bedroom.  No wonder she ran quickly into the house.  Well, there you have the explanation.  I had only my theory to work upon even after Mme. Gobin’s evidence.  But as it happened it was the right one.  Meanwhile, of course, I made my inquiries into Wethermill’s circumstances.  My good friends in England helped me.  They were precarious.  He owed money in Aix, money at his hotel.  We knew from the motor-car that the man we were searching for had returned to Aix.  Things began to look black for Wethermill.  Then you gave me a little piece of information.”

“I!” exclaimed Ricardo, with a start.

“Yes.  You told me that you walked up to the hotel with Harry Wethermill on the night of the murder and separated just before ten.  A glance into his rooms which I had—­you will remember that when we had discovered the motor-car I suggested that we should go to Harry Wethermill’s rooms and talk it over—­that glance enabled me to see that he could very easily have got out of his room on to the verandah below and escaped from the hotel by the garden quite unseen.  For you will remember that whereas your rooms look out to the front and on to the slope of Mont Revard, Wethermill’s look out over the garden and the town of Aix.  In a quarter of an hour or twenty minutes he could have reached the Villa Rose.  He could have been in the salon before half-past ten, and that is just