As you can tell by the summary, this book really leans in to the Gothic Horror tropes. Chatterham Prison broods over the story almost as much as the titular castle in Castle Skull. Rats, bats, and iron maidens can be found within its walls, and the story returns again and again to the precipitous drop from the balcony of the Governor’s Room, down towards the disease-ridden depths of the well. The main corpse is found, of course, by lightning-flash in the midst of a storm. But despite all the doom and gloom, Hag’s Nook is actually Carr’s lightest book yet. He seems to have figured out that All Menace All The Time can leave the tone feeling flat, and Hag’s Nook is loaded with moments of joy or comedy to offset the darkness. Actually, I think he goes too far with the comedy. I can deal with Mrs Fell’s absent-mindedness, or with Chief Constable Sir Benjamin playing wild-theory tennis with our protagonist Tad Rampole. It’s the minor characters I find a bit much, particularly the “comic servant” Mrs Bundle, who’s like a photocopy of a photocopy of Comic Servants in English fiction. The comedy feels better when coming from characters who have other roles in the plot – like Dr Fell, for example.

This is Dr Fell’s introduction, and he seems to wheeze onto the page fully formed. It’s been pointed out elsewhere that Fell has buffoonish elements here that would be more associated with later books featuring Henry Merrivale, Carr’s other main sleuth. I’m not so sure there is a reversal, though. There’s no slapstick escapades, and Fell tends to know when he’s being comic, where Merrivale doesn’t. The most obvious feature of Fell that gets dropped after this book is his interest in arguing obscure points of history. Oh, and the wife. Not sure where she ends up.
Aside from these, Fell is as he always is, avuncular, authoritative, and tuned to the paradoxes that are thrown his way by his unusual cases. When Fell is on the scene, you can breathe a sigh of relief, no matter the tension beforehand.

Those Chesterton-style paradoxes are really tuned up here; Carr has enhanced his method of “flourishing” the clues, by making them form into a mystery of their own:

“What’s this all about?” asked the chief constable. “According to what you’ve told me, young Starberth arrived at the Governor’s room on the tick of eleven – his watch is right – everything is right.”
“Yes,” said Dr Fell. “Yes. That’s what makes it wrong, you see.”

Hag’s Nook is not as dense with mystery as some of the books to come, but it still has more clues than most mysteries by anyone else. Though not all the clues are good – it does also make use of the dusty old trope of (ROT13) gur zbabtenzzrq unaqxrepuvrs!
The crime, while not an impossibility, does have that air of the supernatural that Carr would use again, and the solution also uses a few of the same tricks that he would later use to build up an air-tight impossibility.
The “puzzle” here is not quite a whodunnit – Carr doesn’t hide the culprit by providing a selection of possibilities, instead relying on the complexity of the mystery. I seem to remember this providing a good enough mask when I read this through the first time. The culprit was a good surprise for me then.

One slight disappointment is that the explanation is provided by a confession letter at the end. While this does give us an opportunity to see the killer in their creepy true colours, it also feels like a bit of a cop-out.
On this read, I was also more aware of implausibilities that Carr is able to cover over on the first read through sheer force of pacing and Fell’s compelling phrasing; for example (ROT13) qrfcvgr jung Sryy vafvfgf, nalbar jub pna’g syrr gurve pevzrf jvgu guerr lrnef urnq fgneg zhfg or n irel cbbe pevzvany vaqrrq. That said, this didn’t really affect my enjoyment of the book.
The only other issue (apart from a few misfiring comedy scenes) is when the heroine Dorothy Starberth confesses to Tad her fears that the Starberths might be “damned in the blood”. Carr is not really able to convey her emotional anguish at all, and the worry comes and goes with her so quickly that it feels artificial; a holdover from the melodrama that tinged It Walks By Night.

However, what strikes me whenever I read this book is how fresh it all feels. Sure, there are plenty of well-worn tropes here, especially when it comes to the “Young American” and his romance. But it’s something about Carr’s writing that feels fresh. He’s just started over with a new detective, after seeming to run out of steam with Bencolin. Carr was about to move to England when he wrote the book, and if his passionate description of its charms is any indication, he was excited about the move. He tries a few new things in the book, too – introducing a second narrative perspective for the first time, with a few scenes following the Starberth butler, Budge. The payoff for this experiment works excellently, though as far as I remember he ddn’t try it again very often. At any rate, I think the freshness comes from Carr’s eagerness to start over with more experience, and tackle new challenges.

This book is always a pleasure to read, and that it’s not even close to being one of Carr’s best just shows the heights he would reach later.

Other opinions:

Clothes in Books
The Grandest Game in the World
The Green Capsule Blog
In Search of the Classic Mystery
The Invisible Event
James Scott Byrnside
Mrs. K Investigates
Only Detect
The Reader is Warned
Tangled Yarns
Tipping My Fedora