In the outer reaches of the young Byzantine Empire, a pursuing pack of trackers is about to overtake a lonely outlaw. He attempts to stave off certain death by fleeing into the cruel Sandara Desert. At the end of his strength, far into the sandy wastes he meets an old hermit. In the days following he recovers from his thirst and exhaustion and is more and more amazed by his saviour. Seeing that the old man's prayers can tame even lions, Agabus, the cruel outlaw poses a question to the man whose life he had wanted to end that first day they met: "What should I do to be like you?" Testing whether his wish is sincere, the old man gives him an unusual mission: to find the most precious diamond in the world. Agabus visits far-off places unaware that secretive shamans are tracking him down because of the treasure he carries. In Aksum he makes an unusual friend who tells him where he can find the legendary Dragon Diamond. Beneath the desert, in an underground world, by an enormous fresh water sea they delay the destruction of the mysterious settlement of forgotten Roman citizens. Agabus finally faces the shamans, finds out the secret of his family and his real name. They exchange the desert for a swamp. The splashing of an unsteady boat echoes rather too loudly in the total silence and rouse a creature it would have been better to leave in its deep slumber. Reaching their goal, they realise that nothing is quite what it seems. The Dragon Diamond apparently is not what the old man was asking for. At the end, Agabus has not fulfilled His task in the expected manner.