Find and ReplaceSynopsis :
Christmas 2010: Jo Grant finds herself stuck in a department store elevator with an alien creature called Huxley.
Huxley is a narrator from Verbatim Six. He is here to let Jo revisit the best time of her life – when she was the plucky companion to that eccentric Space/Time traveller known only as... Iris Wildthyme.
Confronted with memories she knows nothing about, Jo agrees to a meeting with Iris inside her transdimensional bus. Together the three of them take a trip back in time: back to the 1970s, to UNIT HQ and a meeting with the only person who knows the whole truth... Casting :
Jo Grant / Iris Wildthyme - Katy Manning
Huxley - Alex Lowe
Source : http://tardis.wikia.com/wiki/Find_and_Replace_%28audio_story%29