It is that he cannot have too little to do with people who are too deep for him and cannot be too careful of interference with matters he does not understand—that the plain rule is to do nothing in the dark, to be a party to nothing underhanded or mysterious, and never to put his foot where he cannot see the ground.
"Esther," Richard resumed, "you are not to suppose that I have come here to make underhanded charges against John Jarndyce.
There are no more uses of "underhanded" in the book.
Show samples from other sources
At this point I played a somewhat underhanded trick on this obliging fellow.
Farley Mowat -- Never Cry Wolf
Then he and Claude hurried up the road, away from T.J. Stacey, who generally overlooked T.J.’s underhanded stunts, shook his head.