Caroline Hartley has a magic key. It has allowed she and her brother Martin to secretly step through an attic door and time-travel back to 1912, at a castle they have been staying at in Central Europe. In the present, their father Chris has had an IT presentation brought forward a week at the United Nations in Vienna. This has resulted in the family leaving the castle early and returning to Bratislava, where Chris lives. The Hartley children would love to return to the castle as soon as possible, as they would like to use Carolines magic key one more time. Both wish to time-travel back to 1912 so that they can go on more adventures with their friends.