Dr Quentin Questa has inaccurately predicted the eruption of a volcano for the last decade. This time, however, he invokes a special science code of honour that brings Brains out to his location. Brains discovers that Questa is right: the volcano is gonna blow!
- Scott Tracy - Rasmus Hardiker
- Virgil Tracy, Gordon Tracy - David Menkin
- John Tracy - Thomas Brodie-Sangster
- Brains - Kayvan Novak
- Grandma Tracy - Sandra Dickinson