Dallas looked at him again, and then, with an incredulous gesture, passed out of sight under the vaulted doorway.
Mr. Welland laid down his knife and fork and looked anxiously and incredulously across the luncheon-table at his wife, who, adjusting her gold eye-glasses, read aloud, in the tone of high comedy: "Professor and Mrs. Emerson Sillerton request the pleasure of Mr. and Mrs. Welland’s company at the meeting of the Wednesday Afternoon Club on August 25th at 3 o’clock punctually.
There are no more uses of "incredulous" in the book.
Show samples from other sources
I find it incredulous that you believe she is sincere.