The Seven Streams by Warwick Deeping

Tristan was still at Agravale with some two hundred men, when a mob of peasant folk came into the city, bringing with them a lean, half-starved southron who had fled to Agravale over the mountains. The man had served as a slave in Serjabil's palace, and being wise as to the Caliph's schemes of conquest, he had dared martyrdom and fled for the north. Two other Christians who had shared his flight had been taken and beheaded on the road. The third had gained the mountains in safety, and having crossed by the pass known as St. Isidore's Gate, had descended into the lowlands with the cry of a prophet-

"Fly, for the Saracens are at my heels!"