My Lady's Money - Wilkie Collins

Lady Lydiard has an uncomfortable bit of business to settle, and intends to do so with a five hundred pound note. But just as she is about to complete the letter with which she is to send the note off, an emergency occurs in the house, and for a little while everyone is preoccupied - be it with the sick dog Tommie, the management of the house, or a kindling love. But when everything settles down again, the note is missing. Who took it? - Summary by Carolin