El hermano del tiempo

In the early 14th century, young Michael O'Muldarry witnesses the death of his mother, who is convicted of practising witchcraft. Escaping the executioners, Michael flees into the woods and vanishes, where he is rescued by monks from a nearby abbey. Intending to conceal his identity, he changes his name to Martin Smith and lives there as a novice until Father James discovers, at almost the same time as Martin himself, the strange anomaly that affects his body: he does not get sick, he does not grow, he does not age.
Convinced that this condition can only bring him trouble, he escapes from the monastery without knowing that running away will be just the start of a long series of events. He will have to keep running forever, either so that those around him do not realise that he never gets old or to escape from those who know about his existence due to Father James' papers. Among the agonies of the medieval plague, on the ships that colonised America, playing female roles in Molière's theatre, in the Japan of the samurais or in Nazi Germany, Martin Smith lives the terrible weight of his immortality with as much dignity as he can.
Meanwhile, in the 21st century, a wealthy American pharmaceutical tycoon who knows his secret puts all the resources at his disposal into finding the formula of Michael's immortality. The chapters alternate between the present (the persecution of Michael) and the past (memories of over six centuries of life).