[TOMT] [BOOK] In what Nero Wolfe story by Rex Stout did this line appear?

[TOMT] In one of the 33 novels and 39 short stories that Rex Stout's character Nero Wolfe appeared, Wolfe made the following statement about his notional solution to a mystery: (words to the effect of) "I have no proof that this is what happened, but I like this explanation because" (more or less exact quote) "it explains everything, and nothing contradicts it" (words to the effect of) "I won't be dissuaded until I am proved wrong." I sure thought that it was in "Murder By The Book" but it's not. Anyone remember what book this line is from, before I have to go through all 33 novels and 39 short stories to find it? Thanks.