He proved the innocence of one before accusing the other.

You can easily believe, Monsieur, that so complicated a scheme as this must have been long and carefully thought out in advance by Larsan.

I can tell you that he had long been engaged on its elaboration.

If you care to learn how he had gathered information, you will find that he had, on one occasion, disguised himself as the commissionaire between the 'Laboratory of the Surete' and Monsieur Stangerson, of whom 'experiments' were demanded.

In this way he had been able before the crime, on two occasions to take stock of the pavilion.