When Diana Bakewell isn't busy guiding tour groups around London or solving mysteries, she enjoys spending time in the garden of Eccleston Square, in front of her Pimlico flat.

But one morning she's chatting with the gardener, Nichola, when they realise that the garden's most beloved ornament is gone - Eccles the Gnome!

Diana's colleague Zaf spots that Eccles has been photographed around London, and is quickly becoming an Instagram star. Can Diana track down Eccles and his kidnapper and return him to his plinth in the garden square?