In the early months of the Spanish Civil War, Canadian-American archaeologist Dr. Grace "Shale" Clifden and her inexperienced field crew of well-met Canadians-Dorothy Livesay, P. K. Page, and Sheila Doherty-are documenting a rare discovery of prehistoric cave art in Galicia when they are kidnapped. A local Spanish commander, a Nationalists, loyal to Franco and the Fascists, believes they are foreign spies and takes them to his ancestral home, locking them in underground cells. There, he enlists his brother, Dr. Alexandre Castro, a psychology professor at the University of Madrid, to interrogate the women, but instead, he secretly forms a bond with them. Unlike the commander, Alexandre is a loyalist, supporting the Republicans, nevertheless, he is eager to escape the clutches of the State Intelligence Service-who plan to force him to devise forms of psychological torture. Alexandre convinces his brother to let him chaperone the women while they finish their research, as the Smithsonian will pay the commander a hefty sum for it. After Shale and the women have compiled their findings, Alexandre helps them escape Spain to London with him. But while in London, they learn of other Canadians who have bravely volunteered to help fight for democracy in Spain despite the dangers, and now, they, too, want to help the cause. Knowing the war is escalating, Alexandre, Shale and the women are determined to rescue archives and artifacts from the University of Madrid and help the National Junta for Protection of Artistic Treasure transfer Spain's great art collection to Geneva. As they do so, they must be braver than ever, as the devastating Battle of Madrid is upon them.