Christmas 2010, and Jo Grant finds herself stuck in a department store elevator with an alien creature called Huxley.

Huxley is a narrator from Verbatim Six, and 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 knew nothing about, Jo agrees to a meeting with Iris inside her transdimensional bus, and 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...