observe! It is no longer any use for him to pretend
that he and his friends did not disappear in that car. The murder is
already discovered, and with the murder the disappearance of the car.
So he no longer troubles his head about it. He does not remove the
traces of mould from the place where his feet rested, which otherwise,
no doubt, he would have done. It no longer matters. He has to run to
earth now before he is seen. That is all his business. And so the state
of the car is explained. It was a bold step to bring that car
back--yes, a bold and desperate step. But a clever one. For, if it had
succeeded, we should have known nothing of their movements--oh, but
nothing--nothing. Ah! I tell you this is no ordinary blundering affair.
They are clever people who devised this crime--clever, and of an
audacity which is surprising."

Then Hanaud lit another cigarette.

Mr. Ricardo, on the other hand, could hardly continue to smoke for
excitement.

"I cannot understand your calmness," he exclaimed.

"No?" said Hanaud. "Yet it is so obvious. You are the amateur, I am the
professional--that is all."

He looked at his watch and rose to his feet.

"I must go" he said and as he turned towards the door a cry sprang from
Mr. Ricardo's lips "It is true. I am the amateur. Yet I have knowledge,
Monsieur Hanaud which the professional would do well to obtain."

Hanaud turned a guarded face towards Ricardo. There was no longer any
raillery in his manner. He spoke slowly, coldly.

"Let me have it then!"

"I have driven in my motor-car from Geneva to Aix," Ricardo cried
excitedly. "A bridge crosses a ravine high up amongst the mountains. At
the bridge there is a Custom House. There--at the Pont de la
Caille--your car is stopped. It is searched. You must sign your name in
a book. And there is no way round. You would find sure and certain
proof whether or no Madame Dauvray's car travelled last night to
Geneva. Not so many travellers pass along that road at night. You would
find certain proof too of how many people were in the car. For they
search carefully at the Pont de la Caille."

A dark flush overspread Hanaud's face. Ricardo was in the seventh
Heaven. He had at last contributed something to the history of this
crime. He had repaired an omission. He had supplied knowledge to the
omniscient. Wethermill looked up drearily like one who has lost heart.

"Yes, you must not neglect that clue," he said.

Hanaud replied testily: