Heyer Challenge #8

This one was easier - got lots of responses:

( Challenge #8 )

So who are X, Y and Z - and Q as well?
Which book?
What, exactly, did Y do to make X think Y deranged?

and the bonus punch - what was Y really doing?

Heyer Challenge #9

Another easy one - from one of my favourites (again):

( Challenge #9 )

Who are X, Y and Z?
Which book?
What has Y been up to?