Valencia thinks Billy is full of secrets that he doesn't want to talk about. (He is, of course: Tralfamadore, time-traveling, and so on.)
Billy has a great idea for what should be written on his tombstone. On the next page, there is an illustration of a tombstone with the words, "Everything Was Beautiful, and Nothing Hurt" (5.51).
Valencia tells him that she once overheard Billy telling her father about the execution of Edgar Derby.
Billy had to bury Derby after he was shot.
Derby didn't really seem scared; they had given him drugs to keep him calm in front of the firing squad.
Billy excuses himself to go to the bathroom and winds up back in 1944.