In November 1944, Nazi Germany unleashes the V-2 ballistic missile against London in a last, desperate bid to alter the course of the war. Robert Harris tells the story from two sides at once: Rudi Graf, a disillusioned German rocket engineer launching missiles from occupied Holland, and Kay Caton-Walsh, a Women's Auxiliary Air Force officer who survives a V-2 strike and is sent to Belgium with a unit of mathematicians tasked with tracing the rockets' launch sites before more of London is destroyed.
As rumours of a defector spread through the German rocket program, Graf comes under suspicion of sabotage, and both he and Kay find themselves, unknowingly, hunting the same person. Harris grounds the chase in the real history of the V-2 campaign — the potato-derived rocket fuel, the radar and trajectory mathematics used to trace the launch sites, and the thousands of slave labourers who died producing the weapon and the civilians it killed in London — building a short, tense thriller out of one of the least-explored campaigns of the Second World War.