The red box

From Wikipedia: "I never knew a plaguier case. We have all the knowledge we need, and not a shred of presentable evidence. Unless the red box is found—are we actually going to be forced to send Saul to Scotland or Spain or both? Good heavens! Are we so inept that we must half encircle the globe to demonstrate the motive and the technique of a murder that happened in our own office in front of our eyes? Pfui!"

— Nero Wolfe in The Red Box, chapter 14 Wolfe and Archie investigate the death of a model who ate a piece of poisoned candy. One of the suspects begs Wolfe to handle his estate and especially the contents of a certain red box. Wolfe is at first concerned about a possible conflict of interest, but feels unable to refuse when the man dies in his office before telling Wolfe where to find the red box. The police naturally think that he told Wolfe somewhat more before dying. This novel presents the series' first instance of a murder taking place in Wolfe's office.