The Teeth of the Tiger

The fortunes of Don Luis Perenna seem set to only increase after the will of his friend, Cosmo Mornington, is read. Perenna stands to benefit by one million francs if he finds the true heir, and by one hundred million if they can’t be found. But after both a detective and a potential recipient of the fortune die in the in the same way as Mornington, Perenna (alias Arsène Lupin) must fight to prove his innocence and discover the real murderer.
The Teeth of the Tiger was published in this English translation in 1914, but wasn’t available in the original French until its serialization in Le Journal in 1920. In the timeline of the series, The Teeth of the Tiger is set after the events of 813, and continues with the rebalancing of Lupin from a god-like genius to a fallible, albeit brilliant, man.
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https://en.wikipedia.org/wiki/Maurice_Leblanc