ared:

"Monsieur le Juge d'Instruction, this is Saturday. I have to be back at
school on Monday evening. Well, if you will have the goodness to be
here at ten o'clock exactly on Monday morning, I will try to give you
the key to the riddle."

"Really, M. Beautrelet--do you think so? Are you sure?"

"I hope so, at any rate."

"And where are you going now?"

"I am going to see if the facts consent to fit in with the general
theory which I am beginning to perceive."

"And if they don't fit in?"

"Well, Monsieur le Juge d'Instruction," said Beautrelet, with a laugh,
"then it will be their fault and I must look for others which, will
prove more tractable. Till Monday, then?"

"Till Monday."

A few minutes later, M. Filleul was driving toward Dieppe, while
Isidore mounted a bicycle which he had borrowed from the Comte de
Gesvres and rode off along the road to Yerville and Caudebec-en-Caux.

There was one point in particular on which the young man was anxious to
form a clear opinion, because this just appeared to him to be the
enemy's weakest point. Objects of the size of the four Rubens pictures
cannot be juggled away. They were bound to be somewhere. Granting that
it was impossible to find them for the moment, might one not discover
the road by which they had disappeared?

What Beautrelet surmised was that the four pictures had undoubtedly
been carried off in the motor car, but that, before reaching Caudebec,
they were transferred to another car, which had crossed the Seine
either above Caudebec or below it. Now the first horse-boat down the
stream was at Quillebeuf, a greatly frequented ferry and, consequently,
dangerous. Up stream, there was the ferry-boat at La Mailleraie, a
large, but lonely market-town, lying well off the main road.

By midnight, Isidore had covered the thirty-five or forty miles to La
Mailleraie and was knocking at the door of an inn by the waterside. He
slept there and, in the morning, questioned the ferrymen.

They consulted the counterfoils in the traffic-book. No motor-car had
crossed on Thursday the 23rd of April.

"A horse-drawn vehicle, then?" suggested Beautrelet. "A cart? A van?"

"No, not either."

Isidore continued his inquiries all through the morning. He was on the
point of leaving for Quillebeuf, when the waiter of the inn at which he
had spent the night said:

"I came back from my thirteen days' training on the morning of which
you are speaking and I saw a cart, but