The prize is a trip for Clyde and his class to see the first showing of Leonardo da Vinci's Mona Lisa in Britain.
She asks the curator Lionel Harding to find the Abomination, which is locked away in a box in the gallery's basement.
Despite his admiration for Mona Lisa, Lionel destroys the key to prevent her from unleashing the Abomination on the world.
The majority of the episode is set in The International Gallery in London, the same gallery where companion Lady Christina De Souza stole the Cup of Athelstan in the Doctor Who episode Planet of the Dead, as the incident was referred to as "the Cup of Athelstan fiasco at Easter".
Pearson Education published a simplified novelisation of this episode by Trevor Baxendale under the title Painting Peril for school literacy programs in September 2010.