Tony Mammoth's life is sweet until his boss and headteacher Mr Cowley is signed off from work with stress. With little sensitivity and thinking purely of maintaining his easy work life, he does whatever it takes to de-stress him and get rid of the younger, popular and eminently more professional temporary headteacher. 

Meanwhile, Mel arranges a big 18th-birthday party for Theo, who desperately wants his mum to stop treating him like a four-year-old.