In Rome, the day after the great fire of July 64, Emperor Nero was in doubt. Lucius Murena, his friend, disappeared. Would he have participated in a plot against him, as some claim? Nero believed, but no longer knows what to think. Lucius's absence range him, as if his own past had disappeared, too. Lucius is in the hands of a woman, Lemuria, who drugged him in order to make him the object of his pleasure. Lucius decides to flee her, because he must regain his freedom to find himself. But his memory is uncertain. Only Petrone can help him to reconnect with him.