Molly examines her shelf of special things at the back of Mack's stall. She chooses the key and remembers the day she got it... \n\nThe Lord Provost is coming to visit today, so there is lots of tidying and sorting to be done. While clearing up, Moira leaves the key to her office on a table and it gets tidied away in a pot. Later, the adults gather in Moira's office. Mack accidently slams the office door shut, and without the key they can't get out. Luckily, Molly has an idea. Mack and the kids can give the Lord Provost a tour of the Big Hub!