I've recently re-read Dead Man's Folly, which, though one of Dame Christie's simplest fare, was certainly quite enjoyable. For those who've read it, the killer (or rather, the accomplice) SPOILER ALERT was not named by Dame Christie at all, was she? She was only referred to as a student or a hitchhiker... I was wondering, as a matter of curiosity, if there were any other killers whose names were never mentioned in the stories they appeared in.
I can think of at least one more...