Katie Morag is looking forward to playing a game of pooh sticks with her mum. It's her favourite game. But Mrs McColl is too busy to play, so Katie Morag stomps off to Grannie Island's house and gets soaking wet on the way. Grannie Island gives her some spare wellies that she happens to have, which once belonged to a girl called Izzy. Katie Morag is curious because she doesn't know an Izzy, so she and Grannie Island travel all over the island to see if they can find her.