Wolfpack Across the Wall - Billy Love's Novels, #6

In the sixth book of the BIlly Love novel series, the Forsaken Children, now young adults, find themselves in the midst of the mid-sixties Cold War between East and West. Their common German-American background and their imperfect, invincebale friendships with each other leads them on a mission that takes them across the Iron Curtain into East Germany and Russia. The Wolfpack, as they are known, embark on a journey that straddles both worlds.
Nurse May Phillips has been arrested, charged with spying on the Russians, and is incarcerated in a prison in East Germany. She holds many of the answers to the foursome's questions. As Ursula, Renata, Wolfgang and Ruth enlist the help of many, including celebrities, to free her, they come together through remarkable resilience and determination.