A source of fabulous power in the heart of an enemy's kingdom.

AD 273.

Obsessed by the solar religions of the east, the emperor Aurelian sets out to obtain every sacred object within his realm. But one - a mysterious rock said to channel the power of the sun god - lies beyond his reach. Warrior-priest Ilaha has captured the legendary stone and is using it to raise an army against Rome.

For Imperial agent Cassius Corbulo and ex-gladiator bodyguard Indavara, stopping him constitutes their greatest challenge yet. Assisted by a squad of undercover soldiers and a Saracen chieftain, they trek south across the deserts of Arabia, encountering sandstorms, murderous money-lenders and a ruthless German mercenary.

And when they finally reach Ilaha's mountain fortress, they face thousands of warriors who will give their lives to protect him ... and the black stone.