Basically ignored during its publication and then out of print although still enjoying strong reviews and a cult following by those who have read it, the novel is the portrayal of an English-born man, David, who is captured as a very young child and sold into slavery to Baibars, a Mamluk officer.

He is sent to the Papal Court in Orvieto in the 13th century as a spy, in order to foil an alliance between the Christian West and the Mongolian descendants of Genghis Khan to exterminate the Muslim faith and capture the Holy Land.

Many of the characters in the novel, such as Thomas Aquinas, Baibars, King Manfred of Sicily, Louis IX, and Charles of Anjou, are historical figures, who are woven into the fictional canvas Shea invented.

Some historians believe that an alliance was attempted by the Papal Court, with Louis IX's backing, with the Mongols against the Muslim world, which ultimately failed.

Other major fictional characters include Sophia, a Byzantine woman who is a member of Manfred's court and Manfred's former concubine and accompanies Daoud on his mission, and Simon de Gobingnon, a French knight assigned to protect the Mongol ambassadors, who is Daoud's chief nemesis and the son of the major characters in Shea's All Things Are Lights.