Xena and Xander Holmes think living in London will be boring. But one afternoon, they're handed a cryptic note that leads them to a hidden room - and a secret society. When they discover they're related to Sherlock Holmes and inherit his unsolved casebook, life becomes so much more exciting. The siblings set out to solve the cases their famous ancestor couldn't, starting with the mystery of a prized painting that vanished more than a hundred years ago. Can two smart twenty-first century kids succeed where Sherlock Holmes could not?