This the story of the career of a young Briton, who has been held hostage by the Romans for five years following a revolt by the tribal leader Caractacus. He uses his time under Roman authority to learn Latin and Roman history and military tactics & discipline. He then applies his knowledge during the Iceni revolt under Queen Bodacia, which is eventually brutally syppressed.
During the revolt, several Roman towns are taken and sacked, and the Iceni slaughter all the inhabitants, except Beric's Roman tutor and the daughter of his Roman "host", whom Beric has taken from the city of Camelodunum before its capture. Beric arranges for them to be restored to their liberty following the defeat of Quenn Bodacia's army and her and her attendants', including Beric's own mother's, subsequent deaths by poison to avoid being taken captive by Rome.
Following the revolt he and his followers take to the fenland and conduct a guerilla campaign against the Roman forces, with Beric acknowledged as the new leader of the Iceni even at the young age of 18. His band is taken through treachery, and he and his last two dozen followers are taken prisoner and sent as captives to Rome, but not before he arranges amnesty for the rest of the Iceni with the new Propraetor (Governor) of Briton.
On his way to Rome he is befriended by one of his guards and by a Roman family in Massilia. He and his followers are sent to be schooled as gladiators, where their physiques bode well to make them outstanding performers in the arena.
He learns that his friends from Massilia have returned to Rome and that one of their daughters has become a Christian convert despite Nero's persecution and the risk of death. When she is condemned to death in the arena at the teeth and claws of a lion, Beric leaps to her side and offers to be her champion. Nero agrees to release the girl if Beric should defeat the lion, but orders that he face the lion unarmed, which amounts to a death sentence.
Beric however, manages to subdue the lion using his clothing as an improvised net, and wins his freedom from the astonished and enthusiastic crowd.
Nero subsequently has him installed in the palace as his personal "librarian", to avoid provoking the Praetorian Guard's jealousy over their priviledge as Caesar's bodygaurds, while in reality Beric (along with the rest of his fellow Britons) will now serve as a personal bodyguard, loyal only to Caesar and completely isolated from any hint of court intrigue.
Beric eventually is betrothed to the sister of the girl he saved in the arena, and is forced to defy Caesar's insistance that she be invited to attend one of his notorious bacchanalian feasts. Knowing of Nero's treacherous nature, Beric had an escape plan. When Nero orders his arrest, he and his fellow Britons fight their way out of the palace, while his betrothed takes refuge in the catacombs with the Christians.
They hide out in the hills where they combine forces with other escaped slaves, including other gladiators. The Roman army attempts to cut off their escape but Beric's use of the same tactics as before in the fens of Briton causes the Romans to suffer several times as many casualties as the fugitives. He is even able to reunite with his fiance and formalize their marriage.
The leader of the Roman forces is the same man who was his host in Briton and whose daughter was the girl Beric had rescued from the sack of Camelodunum, and who was now married his second in command, the former guard who had befriended Beric on the journey to Rome.
When Nero takes his own life after Galba is chosen by the army as the new Caesar, Beric and his band of fugitives are offered amnesty and free passage back to their homelands, where Beric is able to unite the Britons in anticipation of a prosperous and peaceful future as loyal Roman subjects.
At the end of the story, the author acknowledges that this will all be for nought when Rome's decline leads it to withdraw its legions leaving Briton exposed to the depredations of the Vikings and other raiders.