When the voices of the UK's biggest pop stars turn into high-pitched squeals overnight, the Spy School cadets are tasked with discovering what could be causing it. Evil Goldfist's plot to end the singing careers of pop stars leads the cadets to London's O2 Arena in a race against time to save the pop world from disaster!

Evil mastermind Goldfist is behind a cunning plan to interfere with London's waterways - can the Spy School cadets crack the right codes to stop him? Their mission takes them to the London Aquarium, where they come face to face with a creature from the deep.