Barnaby and Winter look at a map showing the location of the cancelled party. This was an Ordnance Survey 1:25000 map of Watlington, with its real name blanked out and "Causton" printed in its place.
Eleanor Bron has played a different character in a previous episode. She played Lady DeQuetteville in season 15: The Dark Rider (2012).
Clare Holman has appeared twice before in the series as Rose Southerly and Sue Tutt, first starring in a 2002 episode.