In 1846 Darwin has a secret: an essay sealed in an envelope and locked in his study drawer which will overturn human understanding of time and nature for ever.

Before he publishes he has just one more riddle to solve, that of the strange anatomy of a barnacle, nick-named Mr Arthrobalanus, found in South America during the voyage of The Beagle. Aberrant creatures like these are the key to the processes of natural selection, but eight years later, with a study filled with hundreds of barnacle specimens, the case is still unclosed.

Was Darwin hesitating? Or was he testing his 'dangerous idea' to destruction? Darwin and the Barnacle is the beautifully written story of how genius sometimes proceeds through indirection - and how one small creature finally proved the theory behind history's most spectacular breakthrough.