1936. Spain erupts in civil war. The Republic forms an International Brigade and calls for volunteers to combat a Nationalist uprising led by General Franco.

After his best friend Jimmy is killed by a police baton on a hunger march to London, Glaswegian Robbie Gillan has a fist fight with the mortician. The police are called and sympathetic nurse Alice Sheridan gives Robbie £5 when he tells her he wants to join the battle in Spain.

Alice's twin brother Simon argues with his father over Spain and leaves on the night ferry for Paris where the volunteers are gathering. In a knife fight with Franco loyalists, Robbie Gillan saves Simon's life and the two men, opposites in class and temperament, cross France and climb the Pyrenees to Spain. Alice, drawn by emotions that are not entirely clear to her, soon follows with the Red Cross.

The battle cry of the Spanish Republic was No pasarán. Pasaremos. They shall not pass. We Shall Pass - the defining spirit of this gripping novel that takes us into the heart of war and reveals the enduring power of love, hope and defiance as Robbie and Alice must overcome every obstacle to be together.