three hearts and three lions by poul anderson

Once the sword is recovered, Holger discovers he is the legendary Ogier the Dane, a champion of Law. However, the decision would be taken out of his hands. But with the perilous Wild Hunt on their tracks, Holger and Alianora pledge their love and he promises, if surviving the ordeal ahead, to remain always with her. However, Holger avoids physically consummating this love – though Alianora wants him to – as he intends to return to the 20th century world he came from. While on this perilous quest, Holger and Alianora fall deeply in love with each other. The sword is in a ruined church, guarded by a nixie, cannibal hillmen, and – most dangerous of all – a troll.

Based on the advice of the wizard, Martinus Trismegistus, they set out to recover the sword Cortana. They escape and, after encountering a dragon, a giant, and a werewolf, reach the town of Tarnberg, where they are joined by a mysterious Saracen called Carahue, who has been searching for Holger. Holger learns that Morgan Le Fay, his lover in a forgotten past life, is his ultimate adversary. They are induced to follow the seemingly attractive elvish Duke Alfric of Faerie, who in fact plots to imprison Holger in Elf Hill, where time runs differently. Seeking to return to his own world, Holger is joined by Alianora, a swan maiden, and Hugi, a dwarf. He finds the clothes and armor fit him perfectly, and he knows how to use the weapons and ride the horse as well as speak fluently the local language, a very archaic form of French. The shield is emblazoned with three hearts and three lions. He finds the equipment and horse of a medieval knight waiting for him. This world is divided between the forces of Chaos, inhabiting the 'Middle World' (which includes Faerie), and the forces of Law based in the human world, which is in turn divided between the Holy Roman Empire and the Saracens. With a German force closing in, Carlsen is shot – and suddenly finds himself transported to a parallel universe, a world where northern European legend concerning Charlemagne ('The Matter of France') is real.

At the shore near Elsinore, he is among the group of resistance fighters trying to cover the escape to Sweden of an important scientist (evidently the nuclear physicist Niels Bohr). Holger Carlsen is an American-trained Danish engineer who joins the Danish resistance to the Nazis in World War II. Three Hearts and Three Lions by Poul Anderson

Three hearts and three lions by poul anderson