As he drove to the prison Coquenil thought with absorbed interest of the test he was planning to settle this question of the footprints.  He was satisfied, from a study of the plaster casts, that the assassin had limped slightly on his left foot as he escaped through the alleyway.  The impressions showed this, the left heel being heavily marked, while the ball of the left foot was much fainter, as if the left ankle movement had been hampered by rheumatism or gout.  It was for this reason that Coquenil had been at such pains to learn whether Kittredge suffered from these maladies.  It appeared that he did not.  Indeed, M. Paul himself remembered the young man’s quick, springy step when he left the cab that fatal night to enter Bonneton’s house.  So now he proposed to make Lloyd walk back and forth several times in a pair of his own boots over soft earth in the prison yard and then show that impressions of these new footprints were different in the pressure marks, and probably in the length of stride, from those left in the alleyway.  This would be further indication, along with the differences already noted in the nails, that the alleyway footprints were not made by Kittredge.

Not made by Kittredge, reflected the detective, but by a man wearing Kittredge’s boots, a man wearing the missing third pair, the stolen pair!  Ah, there was a nut to crack!  This man must have stolen the boots, as he had doubtless stolen the pistol, to throw suspicion on an innocent person.  No other conclusion was possible; yet, he had not returned the boots to Kittredge’s room after the crime.  Why not?  It was essential to his purpose that they be found in Kittredge’s room, he must have intended to return them, something quite unforeseen must have prevented him from doing so. What had prevented the assassin from returning Kittredge’s boots?

As soon as Coquenil reached the prison he was shown into the director’s private room, and he noticed that M. Dedet received him with a strange mixture of surliness and suspicion.

“What’s the trouble?” asked the detective.

“Everything,” snarled the other, then he burst out:  “What the devil did you mean by sending that girl to me?”

“What did I mean?” repeated Coquenil, puzzled by the jailer’s hostility.  “Didn’t she tell you what she wanted?”

Dedet made no reply, but unlocking a drawer, he searched among some envelopes, and producing a square of faded blotting paper, he opened it before his visitor.

“There!” he said, and with a heavy finger he pointed to a scrawl of words.  “There’s what she wrote, and you know damned well you put her up to it.”

Coquenil studied the words with increasing perplexity.  “I have no idea what this means,” he declared.

“You lie!” retorted the jailer.

M. Paul sprang to his feet.  “Take that back,” he ordered with a look of menace, and the rough man grumbled an apology.  “Just the same,” he muttered, “it’s mighty queer how she knew it unless you told her.”