In this episode, Si welcomes his friend Mark Dodyk into the Library of Impossible Things.

What will Mark bring to go into the Library? How was his childhood neighbour responsible for making him a fan? What words could you whisper into Mark's ear to make him go all weak at the knees? How much was Doctor Who a comfort to Mark when he was growing up?

Take another trip into The Library to find out the answer to these questions and more!