But he was not for a single instant the dupe of her blundering alacrity; he knew that of what she promised she was competent to perform but an insignificant fraction, and the more she professed her willingness to serve him, the greater fool he thought her.
There are no more uses of "dupe" in the book.
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The immigrant was duped because he trusted everyone
She is innocent. She was duped like the rest of us.