It's John's birthday and he has decided to do something different this year - a murder mystery party, where all the couples have to come in fancy dress as characters in the mystery. Soon, however, there is a real life mystery: is it Maureen or her alter ego Lady Greystoke that's having an affair? Will Alan's success at re-gifting eventually come back to haunt him? And who is the exotic-sounding 'Diego'? John just wants someone to take the game seriously.