Murder at Maddingly Grange: Inspector Barnaby #5 First edition

Simon Hannford is in need of some fast money, and murder seems the obvious solution. Specifically, a 1930s Murder Mystery Weekend, to be held at Madingly Grange, his aunt's superbly hideous gothic mansion. Simon and his sister are meant to be house-sitting, but surely Aunt Maude would not begrudge them the chance to earn a few nearly honest shekels. Simon's grand plans quickly go awry, beginning with the guests?each one dottier than the last?and moving on to the staff, hired on the cheap and with larcenous plans of their own. And when an actual body turns up, Simon's charade of detection is suddenly forced to begin in earnest.