Inference clear as day in this region of suspicion, that Mr. Barsad, still in the pay of the aristocratic English government, is the spy of Pitt, the treacherous foe of the Republic crouching in its bosom, the English traitor and agent of all mischief so much spoken of and so difficult to find.
There are no more uses of "treacherous" in the book.
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The road through Afghanistan’s Kabul gorge is even more treacherous than the Road of Death in Bolivia.
It’s a gorgeous beach, but the waves are treacherous in the water.