After spending some time eating school dinners, Horrid Henry is happy to be going back to having Packed Lunches for dinner time at school. But when he goes back to the Packed Lunch room for the first time in a while, he meets his new enemy - Greasy Greta, the Demon Dinner Lady. She uses the rule of 'No Sweets In School', by eating any sweets the children brought in their packed lunches. The only way to stop her is by playing her at her own game...