This is book 1 of the "Lord Peter Wimsey" series.

This note contains spoilers for the book.

Haven't read this in ages. A gorgeous mystery, starting with an unknown body turning up in the bathtub of an architect.

This also has a number of fairly nice bits of Peter being the loon; if not to the extent as in Murder Must Advertise. Which, now that I think about it, I should reread soon. Also some time with Peter being conflicted about the morality of his hobby.

I'm sure Sayers meant considerable weight to attach to the actual murderer being the atheist doctor. But it doesn't bother me that much; atheists are as likely to be crazy as anybody else, so why not?