The Hundred-Towered City

What awaits Jack, Annie and Davey when they are transported back in time to the gothic city of Prague, to search for their missing parents? Trying to avoid capture by the secret police, they find themselves running through dark and dangerous cobbled streets and meet some very shady characters. Where are their parents and who has stolen the key to the time machine? Alchemists, mythical creatures and a man with a hook for a hand hold the answers they're looking for. Will our young heroes be in time to save their parents from eerie Karlstein Castle? And even if they do, how will they return to the present day without the key?