The story begins in 1227 after the death of Genghis Khan. Khan's three sons now rule his lands and, against their father's final wishes, they desire war with the West. They attack a western kingdom and kill its king.
The young Prince Alexander escapes and Hercules encounters him in the forest. He tells the hero that his sister, Princess Bianca is being held captive by the Mongols.
Hercules arranges to have himself captured so he can get close to the princess. Then the hero faces the brothers in a series of challenges. When he is victorious, he trades his freedom for that of Bianca. The brothers release her but treacherously re-capture her. Hercules must then escape and with the help of a nearby army, he frees Bianca and reunites her with Alexander.
I love the costume design in this film. There's a lot of attention to detail and a great variety of costume styles. It's kind of weird to see Hercules paired with a medieval army but somehow it sort of works. Mark Forest makes a great Hercules which is probably why he starred in 12 sword and sandal films. This is not one of the more stellar Hercules films but it's not bad. And it features a giant grist mill: foreshadowing Conan?