The friendship of two 10-year-old English girls is tested when one travels through a portal to the future. In 1940, food rationing and fear of bombs are the backdrop for best friends Lottie and Kitty, who care more about anagrams and playing make-believe than the war. Lottie's scientist father researches time travel, work that's governed by the Official Secrets Act and coveted by the Nazis. The girls are kidnapped and taken to a cellar where Germans are trying to coerce Lottie's father into revealing his research. Lottie sees a shimmering portal and leaps through just as shots are fired, landing in a small Wisconsin town in 2013. She's befriended by a helpful librarian and a boy her own age named Jake. The passage of three years confirms her father's hypothesis that there is no returning to her own time. Lottie adjusts to a new school and life with a foster family, when she finds a postcard from Kitty addressed to her and stuck in a library book, raising her hopes that her friend is still somewhere to be found. Lottie's first-person account has a lighthearted tone, with lots of dialogue and details contrasting childhood in wartime England with modern-day America. Her transition to her new life is awkward but realistic, and the focus of this charming novel is always on friendship and loyalty. Rewarding and uplifting.