“Dash it all!” said Mazeroux once more.  “It was not worth troubling about the poor devils and performing such miracles to save them!”

The exclamation conveyed a reproach.  Perenna grasped it and admitted: 

“You are right, Mazeroux; I was not equal to the job.”

“Nor I, Chief.”

“You ... you have only been in this business since yesterday evening—­”

“Well, so have you, Chief!”

“Yes, I know, since yesterday evening, whereas the others have been working at it for weeks and weeks.  But, all the same, these two are dead; and I was there, I, Lupin, was there!  The thing has been done under my eyes; and I saw nothing!  I saw nothing!  How is it possible?”

He uncovered the poor boy’s shoulders, showing the mark of a puncture at the top of the arm.

“The same mark—­the same mark obviously that we shall find on the father....  The lad does not seem to have suffered, either....  Poor little chap!  He did not look very strong....  Never mind, it’s a nice face; what a terrible blow for his mother when she learns!”

The detective sergeant wept with anger and pity, while he kept on mumbling: 

“Dash it all!...  Dash it all!”

“We shall avenge them, eh, Mazeroux?”

“Rather, Chief!  Twice over!”

“Once will do, Mazeroux.  But it shall be done with a will.”

“That I swear it shall!”

“You’re right; let’s swear.  Let us swear that this dead pair shall be avenged.  Let us swear not to lay down our arms until the murderers of Hippolyte Fauville and his son are punished as they deserve.”

“I swear it as I hope to be saved, Chief.”

“Good!” said Perenna.  “And now to work.  You go and telephone at once to the police office.  I am sure that M. Desmalions will approve of your informing him without delay.  He takes an immense interest in the case.”

“And if the servants come?  If Mme. Fauville—?”

“No one will come till we open the doors; and we shan’t open them except to the Prefect of Police.  It will be for him, afterward, to tell Mme. Fauville that she is a widow and that she has no son.  Go!  Hurry!”

“One moment, Chief; we are forgetting something that will help us enormously.”

“What’s that?”

“The little drab-cloth diary in the safe, in which M. Fauville describes the plot against him.”

“Why, of course!” said Perenna.  “You’re right ... especially as he omitted to mix up the letters of the lock last night, and the key is on the bunch which he left lying on the table.”

They ran down the stairs.

“Leave this to me,” said Mazeroux.  “It’s more regular that you shouldn’t touch the safe.”

He took the bunch, moved the glass case, and inserted the key with a feverish emotion which Don Luis felt even more acutely than he did.  They were at last about to know the details of the mysterious story.  The dead man himself would betray the secret of his murderers.