In the time of the crusades, a Saxon youth is forced to run away from England. He goes with his loyal retainer who brings along a British long bow. The two go all the way to China where they become involved in intrigues in the court of Kubla Kahn.

In the thirteenth century, two hundred years after the Norman Conquest of England, a fierce enmity still exists between Saxon and Norman. Saxon Walter of Gurnie is summoned from his studies at Oxford to the late Earl of Lessford's castle. Walter is the earl's illegitimate son, and because he believes that the earl's Norman wife prevented his father from marrying his mother, Walter hates the Normans above all else. Although the will reveals that the earl has left all his major possessions to his wife and lawful son, Edmond, he does acknowledge Walter as his son. He also bequeaths Walter a pair of boots and wills him into the service of King Edward I. When Walter loudly announces his opposition to the Norman king, Edward, who is also present, attempts to end the bitterness between Saxon and Norman and frees Walter of his obligation. Walter then proceeds to Gurnie, his childhood home, where only his grandfather Alfgar now lives. Because he believes the earl acted dishonorably toward his daughter, Walter's mother, Alfgar has sworn never to speak with anyone sharing the earl's blood, including Walter, and will only converse with him through a servant. Walter has been preceded by Friar Roger Bacon, who hopes to persuade him to resume his studies. Although he fails, Bacon mentions the distant land of Cathay, rich in gold and knowledge. Later that night, Walter aids a group of Saxons, led by his old friend Tristram, in a successful attempt to gain the release of some Saxon prisoners from the earl's dungeon. While in the castle, Walter claims his father's boots. In one, Walter finds a letter from his father, stating that he has left a small cache of gold in a secret place. Walter then determines to leave England with Tris to seek their fortunes in Cathay. Using the last of the earl's funds, Walter and Tris acquire a place on a caravan bringing gifts to the Kahn and guarded by General Bayan. Bayan is greatly impressed by Tris's ability as an archer and by Walter's skill at chess. Later, Lu Chung, the caravan master's servant, asks them to help Maryam, known as the "Black Rose," who wants to escape from the caravan and go to England. When Walter seems disinclined to help her, she maintains that her English father promised her God would provide a miracle to convey her to England, and she believes Walter is that miracle. Walter scoffs at her desire, but Tris speaks feelingly of the country's great beauty. As they near China, Bayan wages a brutal attack, killing men, women and children. Tris is sickened by this, so when Bayan moves south into China, Walter helps Maryam and Tris to escape. As punishment, Bayan sentences Walter to a trial by gauntlet, which he survives. Bayan then sends Walter as an emissary to the Chinese empress with orders to persuade the Chinese to surrender in the face of Bayan's great strength. At the palace, Walter finds Maryam and Tris. The Chinese believe that the presence of two "pale gods" fulfills an ancient prophecy and portends China's success in battle. While the war rages, Walter discovers the many advances China has made, including the manufacture of paper, printing and gunpowder. When the Chinese continue to lose their war against Bayan, however, Walter and Tris are threatened with death. By now, Walter and Maryam are in love. One night, wearing jewel-laden clothing and carrying samples of Chinese books, a compass and gunpowder, the three head for the river. They are ambushed before they reach safety, and Walter uses the gunpowder to clear their way. Tris is fatally injured in the explosion, and while Walter attempts to save him, he and Maryam become separated. Much later, Walter returns penniless to England, so delighting his grandfather that he forgets his vow never to speak to him. Walter recounts his adventures and reveals that he has left the Chinese inventions with King Edward. Later, the king arrives at Gurnie and Walter admits that Tris's love for England persuaded him that he is English first and Saxon second. Edward knights Walter and presents him with a coat of arms that contains a longbow in honor of Tris. To make his happiness complete, some of Bayan's warriors then appear with Maryam and the jewel-filled jacket he left behind in China.