A gladiator gets caught up in a slave revolt and the invasion of England.

Maximus, governor of a Roman colony in northern Spain in 96 A.D., is building roads and bridges to solidify the Roman holdings against the aggressive Celts, who are led by Malendi and his son, Luna. When the Celts start an avalanche to destroy a bridge built by Lacer, an architect-slave, they are repulsed, and Luna is captured. An emissary from the Roman emperor tells Maximus that the emperor is dying and that Maximus can become the new emperor if he has enough gold. Maximus, intending to obtain the gold in Celt-controlled Valley of the Sil, frees Luna and makes a truce with Malendi. Malendi allows a small force of Romans, supervised by Lacer and accompanied by a small force of Celts, to enter the valley to mine the gold on the condition that Maximus keep his troops away. But Maximus plans to kill Lacer after he obtains the gold because Penelope, Maximus' favorite, is in love with Lacer. She follows Lacer to warn him; Maximus breaks the truce and sends troops into the valley. The Celts attack and Lacer opens the sluice gates of the dam he had engineered to allow the mining. The Celts are drowned in the rising water while Lacer and Maximus battle atop the sluice gate. Maximus is killed, and Lacer and Penelope are given their freedom and depart for a new life in Gaul.