A stunning, exciting story from acclaimed author Dan Smith - author of the Carnegie Medal-nominated Nisha's War.

Berlin, 1961. Anja and Monika are best friends – they even share a cat called Otto.

When a huge barbed wire fence is built between their apartment blocks, everything changes; their city and family are divided by the Berlin Wall.

In the West, Anja is sure it will be taken down, but Monika is afraid. Her world is changing: neighbours keep disappearing, others become spies and shadowy threats lurk around every corner.

Then, Anja discovers that Otto has found a way across. And if he can reach Monika, so can she ...