Andalusia, 1938. The Spanish Civil War is coming to an end. A handful of communist-Stalinists, driven by their enemy - the Spanish fascists - into a small town, take hostages and lock them in a beautiful old cathedral. The communists plan to blow up the temple, destroying as many enemies as possible. It seems that the imprisoned people do not have the slightest chance of survival, but one of them, a former minister and expert on the Middle Ages, Professor Pinson, falls into the hands of a manuscript of a Jewish alchemist, kept in an 11th-century mosque hidden under the cathedral. And this book gives people the key to freedom; however, not everyone will be able to enjoy it...