The Wollestonecraft Girls embark on their most important case yet—the famed dinosaur fossil hunter Mary Anning is being blackmailed. Her precious dog has been snatched and the kidnappers are demanding that Miss Anning authenticate some fake dinosaur bones up for auction at the British Museum in order to get him back. Ada and Mary have just three days to track down the fossil fakers, find the dog, and save the integrity of science!

The game is truly afoot in this quirky caper involving blood-sucking leeches, an asthmatic pug, smoke bombs, secret elevators, diabolical disguises, and wicked word-play.