The letters tell Ginny where to go on each leg of her trip. Sometimes Peg gives Ginny challenges she must accomplish before she can open the next letter. Peg also includes several stipulations. Ginny may only bring what fits in a backpack. She may not bring guidebooks or foreign language books of any kind. She may not bring any electronic devices or use phones and may only communicate with people in the U.S. using letters or postcards.

Ginny convinces her parents to let her go. When she arrives in London, she follows Peg’s directions to a home owned by a man named Richard. He shows her to the room Peg used to rent from him, and Ginny enjoys seeing her aunt’s artwork on the walls.

Richard works at Harrods department store. In order for Ginny to open her next letter, she must find out what Richard sold to the queen. Richard tells her the queen once came for a private fitting at Harrods, and he had to find underpants for her. The word pants turns out to be the ATM pin that allows Ginny to access her aunt’s bank account.

The next letter instructs Ginny to become a mysterious benefactor to a starving artist who deserves a break. Ginny decides on a young man a few years older than her named Keith. Keith is a thespian who has written and produced a play called “Starbucks: The Musical.” It’s not very good, but Ginny is intrigued with him and buys out the rest of his shows with Peg’s money.

Keith sits down next to Ginny after a show and asks why she bought the tickets. She doesn’t explain her aunt’s envelope game until later, but she does go with Keith to have a drink. When Ginny opens the next letter, which instructs her to go to Scotland to meet one of Peg’s painting mentors, Ginny invites Keith along.

They meet Mari, who is a well-known artist. She has a house full of strange items and instructs Ginny to remove her shirt so she can paint a tattoo on her. On the train ride home, Keith reveals that he got a former girlfriend pregnant. Keith produces a wind-up toy that he pilfered for Ginny from the strange artist’s home. Ginny is angry that he stole something from her aunt’s friend. They argue and part on bad terms.

Ginny’s next letter tells her to go to Rome and visit the temple of the vestal virgins. She’s also supposed to ask a Roman boy out for cake. When one named Beppe saves her from being robbed by gypsy children, she asks him out. He takes her to a home he claims is his sister’s and gives her wine. They begin kissing, and he tries to unbutton her shorts. She runs away, rips the button from her shorts, and gives it to the vestal virgins as an offering.

Another letter instructs Ginny to take a train to Paris. After visiting the Louvre, she reads Aunt Peg’s letter about the time Peg spent redecorating someone’s French café. It takes some detective work, but Ginny is finally able to find the café where her aunt lived and worked for a time. When Ginny returns to her hostel, Keith is waiting for her. She’d sent him an email with her location, and he had serendipitously gotten a booking in Paris for his show.

Aunt Peg sends Ginny to Amsterdam next. She tells Ginny to visit someone named Charlie who will show her around. She also tells Ginny to see a painting called “The Night Watch” and to ask someone named Piet about it. The Amsterdam trip is strange and disjointed. Charlie no longer lives at the address Peg left. Ginny’s first hostel is a flea trap, and she quickly vacates. She almost doesn’t find a place to stay and ends up sharing space at another hostel with an energetic American family. She finds a guard named Piet at the museum where the painting resides, but he has nothing remotely interesting to share about the artwork.

Ginny moves on to Copenhagen, where she spends a short time with Peg’s enthusiastic friend Knud on his houseboat. Aunt Peg’s letter explains that she’s having Ginny retrace her steps on the journey of self-discovery she (Peg) made. Ginny finds a hostel and meets a group of Australian students who invite her to hang out with them. They drink a lot. Ginny’s next letter directs her to take a boat to Greece, and her Australian friends decide to join her.

After the long train trip and boat ride, Ginny and the Australian girl, Carrie, swim naked on the beach. They leave their backpacks with the Australian guys, who are sleeping off a hangover. Someone steals the girls’ backpacks. Carrie’s passport is gone, and she wonders how she’ll get home. Ginny loses everything but her passport and bank card. Her last letter from her aunt is gone forever. Ginny can’t get any more money from the ATM, so she calls Richard in London. He tells her to get to the airport and buys her a ticket back to London.

When he picks her up, he reveals that he and Peg were married to make things easier as her medical condition deteriorated. This information makes Peg’s death suddenly real to Ginny, and she runs away. She runs back to Keith’s, and he insists she needs to get in touch with Richard the next day. He says Richard clearly loved and cared for her dying aunt. Keith and Ginny go back to Richard’s the next day. He’s not home, but he’s left a key in case Ginny decided to return.

As Ginny looks around her aunt’s old room, she sees a painting that was very meaningful to Peg. She discovers there’s a key stuck in it. She and Keith go to Harrods where Richard said Peg had used a storage space to paint. With Richard’s help, they find a cabinet containing Peg’s paintings depicting different spots in Europe.

The paintings seem to show the deterioration of Peg’s mind as she was dying. Peg has left instructions for them to send these works to an auction house. A few days later, the paintings are auctioned off for a large sum of money, all of which goes to Ginny. Ginny leaves half of it for Richard. She also tells Richard that Aunt Peg had written in her letters that she loved him. The marriage wasn’t simply one of convenience for her. He is happy to hear this, since he felt the same way.

While Ginny and Keith admit there is something between them, she tells him it’s time for her to go home. She writes a letter to Peg to signal the end of this adventure.