they take the middle of the road?" grumbled the young police agent.

Certainly they could not have crossed to a vacant space as they had done
just before, for on the other side of the street extended a long factory
wall.

"Ah!" sighed Father Absinthe, "we have our labor for our pains."

But Lecoq possessed a temperament that refused to acknowledge defeat.
Animated by the cold anger of a man who sees the object which he was
about to seize disappear from before his eyes, he recommenced his
search, and was well repaid for his efforts.

"I understand!" he cried suddenly, "I comprehend--I see!"

Father Absinthe drew near. He did not see nor divine anything! but he no
longer doubted his companion's powers.

"Look there," said Lecoq; "what are those marks?"

"Marks left by the wheels of some carriage that plainly turned here."

"Very well, papa, these tracks explain everything. When they reached
this spot, our fugitives saw the light of an approaching cab, which
was returning from the centre of Paris. It was empty, and proved their
salvation. They waited, and when it came nearer they hailed the driver.
No doubt they promised him a handsome fare; this is indeed evident,
since he consented to go back again. He turned round here; they got into
the vehicle, and that is why the footprints go no further."