A murder of a Spaniard in Barcelona in 1912 should not have been the interest of anyone in Britain, even if he had been killed in his jail cell. But the man was connected to illegal trade between Spain, Spanish Morocco, and Gilbraltar and the Spanish authorities are worried no one will trust or cooperate with anyone else. Someone impartial is needed so they ask Scotland Yard for assistance and they ask Special Branch who sends Sandor Seymour.