The Doctor, Rose and Mickey goes to investigate Deffry Vale High School, where the students have become super-intelligent and teachers aren't what they seem and lunch times are really peculiar. When the Doctor learns the teachers and the headmaster Lucas Finch are sinister aliens, reuniting with investigative journalist Sarah Jane Smith and mobile computer K-9 mark 3, The Doctor set out to uncover Finch and the teacher's evil intentions and foil their evil scheme.