Reading progress update: I've read 92%.

But it was Sergeant Frant, not Inspector Mallett, who was to make an arrest that day. His incessant labours had borne fruit. They had, to begin with, brought about a considerable liveliness in a quiet part of Yorkshire, involving not only the police, but also doctors, clergymen, registrars and asylum officials.
Hahaha. This little diversion made me laugh because it reminds me of a favourite Christie plot.
As for Tenant for Death, I detected a meandering plot about 33% into the book, but had high hopes that Hare would keep this to a minimum. Meandering plots seem to have been a go to m.o. for GA mysteries, but I am not a fan of the plodding detective story that loses itself in an abundance of red herrings and characters. Unfortunately, Hare's first book seems to have gone down that route, too.
However, I don't remember that either of the other two mysteries I have read by the author suffered from this. On the contrary, I remember enjoying them very much.