Signs of Fire is set in Portugal at the outbreak of the Spanish Civil War. Jorge is a young student on holiday with his uncle in the resort of Figueira da Foz. His uncle shelters two Spaniards, fugitives from the police. Portugal supports Franco: the two men if captured would be returned to certain death. Jorge joins his usual summer crowd of friends. Some of them plot to steal a boat, rescue the Spaniards and smuggle them out of Portugal to join up with the Republicans. Jorge falls in love with Mercedes, the sister of a conspirator, but she is engaged to Almeida, a sailor co-opted to pilot the boat to Spain.