Ginny receives thirteen small blue envelopes from her aunt. Inside the first envelope is a thousand dollars for a one-way ticket to London and a letter explaining a few simple rules. All of Ginny's luggage must fit in her backpack; she is not allowed to use guidebooks, phrase books, a telephone or the Internet. The second is the address of an apartment in London. Ginny must find out the code word from the person who lives there. The next envelope contains a new clue, and so on. Each letter contains an itinerary and instructions, but you can open them one at a time and only after completing the task from the previous envelope. Thanks to these riddles, Ginny goes on a trip to Europe, not realizing what an unexpected gift her aunt has prepared for her.