Why wouldn't Chris sign the check in "The Westing Game"?
Chris knows that once he signs the check and his partner Denton Deere gets his share of the $10,000, he will no longer keep visiting him to play the Westing Game.
Chris, confined to a wheelchair, must spend a lot of time alone in his room, and he gets lonely and bored. He is delighted when he is paired up with Deere for the game; "all he want(s) (is) to play the game with the intern". Chris looks forward to his partner's frequent visits, and spends many hours poring over their clues and "practic(ing) his recitation over and over, hour after lonely hour", so that he can share them with Deere. Chris withholds insights he has discovered about the clues, doling them out one by one, so that "his partner would have to visit him a next time, and a next time". Chris knows that Denton will continue to come and see him and work with him, "as long as he (doesn't) sign the check" (Chapter 14).