In need of a breather, we get back to Flavia de Luce, the precocious 11-year old who loves chemistry and is nosy as all get out. What's not to like about chemistry and nosy, 11-year old girls? My spouse would say, "LOTS!", but I have a fondness for chemistry and I have a fond memory of my awesome niece when she was 11 or so (not that I still don't have a fondness for her now that she's rapidly approaching spinsterhood).
It turns out that Flavia's father finds himself in straightened circumstances, yet again. So he hires out his manor house to a theater company who are planning to film a movie with the most magnificent, illustrious, most beloved actress of the day, Phyllis Wyvern. The film people come and set up. The local vicar convinces Ms. Wyvern that she should put on a small "entertainment" for the people of Bishops Lacey, to support the church's roof restoration project.
It's also Christmas, and Flavia determines to figure out once and for all if St. Nick is fact or fiction. So she concocts an ungodly sticky goo to slather on the chimney pots. She'll capture St. Nick for sure, if he is real, and if she doesn't capture him, then she'll know he's a myth. Yay, experimental science!
Naturally, Phyllis Wyvern turns up murdered just before the local entertainment is to go off. So everyone already had been gathered in the manor house, so they're stuck there. They're also trapped because the roads are all snowed in and the phone lines are down.
Needless to say, Flavia's sleuthing saves the day, and her special goo helps capture one of the culprits, if not St. Nick.