Leo has always been a very happy little boy. But when his beloved Nana dies, he feels very sad. And very worried. What if something happens to him - or his mum and dad? And what if he begins to forget Nana? Mum and Dad say Leo's feelings are normal - but they don't feel very normal to Leo. The last thing Leo thinks he needs is a bunch of fretful furry monsters causing chaos - it's the Worries! But sometimes, Worries are good. Sometimes, they show us that our feelings might be sad and strange, but by paying attention to them, they can help us heal.