They stood back at the door to let the Prefect go first.

“No,” he said, “go on; I’ll follow you.”

He was the last out, leaving the electric light full on.

In the hall he asked the chief detective to blow his whistle.  When all the plain-clothesmen had assembled, he sent them out of the house together with the porter, and shut the door behind him.  Then, calling the detectives who were watching the boulevard, he said: 

“Let everybody stand a good distance away; push the crowd as far back as you can; and be quick about it.  We shall enter the house again in half an hour.”

“And you, Monsieur le Prefet?” whispered Mazeroux, “You won’t remain here, I hope?”

“No, that I shan’t!” he said, laughing.  “If I take our friend Perenna’s advice at all, I may as well take it thoroughly!”

“There is only two minutes left.”

“Our friend Perenna spoke of three o’clock, not of two minutes to three.  So—­”

He crossed the boulevard, accompanied by his secretary general, the chief detective, and Mazeroux, and clambered up the slope of the fortifications opposite the house.

“Perhaps we ought to stoop down,” suggested Mazeroux.

“Let’s stoop, by all means,” said the Prefect, still in a good humour.  “But, honestly, if there’s no explosion, I shall send a bullet through my head.  I could not go on living after making myself look so ridiculous.”

“There will be an explosion, Monsieur le Prefet,” declared Mazeroux.

“What confidence you must have in our friend Don Luis!”

“You have just the same confidence, Monsieur le Prefet.”

They were silent, irritated by the wait, and struggling with the absurd anxiety that oppressed them.  They counted the seconds singly, by the beating of their hearts.  It was interminable.

Three o’clock sounded from somewhere.

“You see,” grinned M. Desmalions, in an altered voice, “you see!  There’s nothing, thank goodness!”

And he growled: 

“It’s idiotic, perfectly idiotic!  How could any one imagine such nonsense!”

Another clock struck, farther away.  Then the hour also rang from the roof of a neighbouring building.

Before the third stroke had sounded they heard a kind of cracking, and, the next moment, came the terrible blast, complete, but so brief that they had only, so to speak, a vision of an immense sheaf of flames and smoke shooting forth enormous stones and pieces of wall, something like the grand finale of a fireworks display.  And it was all over.  The volcano had erupted.

“Look sharp!” shouted the Prefect of Police, darting forward.  “Telephone for the engines, quick, in case of fire!”

He caught Mazeroux by the arm: 

“Run to my motor; you’ll see her a hundred yards down the boulevard.  Tell the man to drive you to Don Luis, and, if you find him, release him and bring him here.”