In the second novel, "Twenty Years After", he has retired from the Musketeers and abandoned his nom-de-guerre of Athos. He has fathered an illegitimate son, Raoul, with Marie de Rohan (Aramis's former mistress) and then adopted the boy, making him the vicomte de Bragelonne. Fatherhood makes Athos a much happier man, but after launching Raoul into a military career, Athos looks for new causes to occupy his life. He embraces the Fronde and then a doomed mission to rescue Charles I of England. He is uncharacteristically terrified by the appearance of Mordaunt, Milady's son, who is attempting to avenge the death of his mother. Athos, despite his reluctance to engage with the son of his ex-wife, ends up forced to slay him in an underwater fight in the English Channel.