Brothers is about life in Roman Britain. It is about betrayal and treachery, stolen gold and hidden treasure, and forbidden love. The brothers in this story are native Britons and Roman soldiers and settlers. Some Britons are farmers and traders while others are rebel warriors who hate the Roman invaders.

In the Roman family, a boy, Gaius Marcius, is given a British slave, Verluccus, for a playmate. Verluccus is branded with a triskele, but he runs away. As a man, he is captured fighting among rebels and returned to Gaius, filled with hatred. Gaius eventually subdues him, and he accepts his lot in slavery. Serving in the household, Verluccus meets Gaia, the sister of Gaius, and they fall in love. But she is soon married to the brother of a man Verluccus is known to want killed. Their love must be secret. They are parted when he goes to Rome with Gaius, and she must remain in Britain with her husband, a Roman military tribune.