Bar the gates, because Parker Pyne is still abroad, flitting here, there, and everywhere in the Middle East. This time we find him in Persia (i.e., Iran)--specifically, the lovely city of Shiraz. But not so lovely as to prevent it from harboring one who is some combination of murderer, lunatic, and/or impostor. Let's sort it out together before our peripatetic PI jets off someplace else for further adventures.
All About Agatha Christie