spy on him anyhow, so he paid just a trifle more than requisite to that
functionary, but not enough to arouse suspicion. Too much is as bad as
too little, a fact that Dupré was well aware of.

He had taken pains to see that his window was directly over the front
door of the café, but now that he was alone and the door locked, he
scrutinised the position more closely. There was an awning over the
front of the café that shut off his view of the pavement and the
policeman marching below. That complicated matters. Still he remembered
that when the sun went down the awning was rolled up. His first idea
when he took the room was to drop the dynamite from the third story
window to the pavement below, but the more he thought of that plan the
less he liked it. It was the sort of thing any fool could do, as the
policeman had said. It would take some thinking over. Besides, dynamite
dropped on the pavement would, at most, but blow in the front of the
shop, kill the perambulating policeman perhaps, or some innocent
passer-by, but it would not hurt old Sonne nor yet the _garçon_
who had made himself so active in arresting Hertzog.

Dupré was a methodical man. He spoke quite truly when he said he was a
student. He now turned his student training on the case as if it were a
problem in mathematics.

First, the dynamite must be exploded inside the café. Second, the thing
must be done so deftly that no suspicion could fall on the perpetrator.
Third, revenge was no revenge when it (A) killed the man who fired the
mine, or (B) left a trail that would lead to his arrest.

Dupré sat down at his table, thrust his hands in his pockets, stretched
out his legs, knit his brows, and set himself to solve the conundrum.