In August 1942, an Egyptian antiquities dealer buys photographs from a South African traitor and passes them on to Field Marshal Rommel. The photos reveal the highly successful weapons trial of a new anti-tank shell, made from an alloy of promethium, that will critically affect the outcomes of the pending tank battles at El Alamein and Stalingrad. The Abwehr dispatches agent Gretchen Konrad to New Zealand to locate the promethium mine. A Nazi agent already in New Zealand manages to acquire a government document that contains the locations of four secret mines. But which is the promethium mine? Gretchen struggles to visit each in turn. Eventually she manages to penetrate the exclusion zone in the southern tip of New Zealand to reach Coopers Island. But have the Allies really found a source of the rare-earth element there? And what effect does the new shell have on the war in the Western Desert and on the Eastern Front in Russia?