Sealed with a Secret: A Wish Novel

When Phoebe finds a beautiful antique at a flea market, she's not sure whether it's as valuable as it looks. But inside she discovers something truly amazing: a letter written during World War II, from a young girl to her sister who's been evacuated from London. The letter includes a "spell" for bringing people closer together, and a list of clues leading all through the city. Each stop along the way adds up to magic.
Phoebe is stunned. Not only has she found a priceless piece of history, the letter is exactly what she needs; she's also separated from her sister, though not by distance. Alice leaves for university soon, but in the meantime, she wants nothing to do with Phoebe. They used to be so close. Now that Phoebe has this magical list, maybe she can fix everything! That is, unless she accidentally makes everything worse instead...
From the author of My Secret Guide to Paris comes an unforgettable trip through London, with secret treasures around every corner