As Mr. Letterblair had said, a wife’s place was at her husband’s side when he was in trouble; but society’s place was not at his side, and Mrs. Beaufort’s cool assumption that it was seemed almost to make her his accomplice.
There are no more uses of "accomplice" in the book.
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Does that make him an accomplice to murder?
Neal Shusterman -- Unwind
One: Go is your accomplice, she was helping you hide this stuff on her property, and in all likelihood, she knows you killed Amy.