Preparations for Sap Day in Treetopolis are thrown into turmoil as the Mushas decide to change the celebration to Stink Day, with stinky fungi that send the smeller to sleep. As his friends fall asleep one by one, it's up to Tom to solve the mystery of the magical sleep, put a stop to the Mushas' mischief and - with Big World Magic help from the audience - to save Sap Day!