Three Hearts and Three Lions

Three Hearts and Three Lions, a fantasy novel by American author Poul Anderson, was published in 1961. It is an expansion of a novella Anderson originally wrote for *Fantasy & Science Fiction* magazine in 1953. The protagonist, Holger Carlsen, is a Danish engineer trained in America who joins the Danish resistance against the Nazis during World War II. While covering the escape of a scientist (likely nuclear physicist Niels Bohr) to Sweden near Elsinore, Carlsen is shot and transported to a parallel universe where Northern European legends are real. In this world, the forces of Chaos inhabit the "Middle World" (including Faerie), while the forces of Law are based in the human realm, split between the Holy Roman Empire and the Saracens. Carlsen finds a medieval knight's equipment waiting for him, including a shield bearing three hearts and three lions, and discovers he can speak an archaic French, ride a horse, and use weapons fluently.

Seeking a way home, Carlsen is joined by Alianora, a swan maiden, and Hugi, a dwarf. They follow the elvish Duke Alfric of Faerie, who intends to trap Carlsen in Elf Hill, where time flows differently. Carlsen learns that Morgan Le Fay, his lover from a forgotten past life, is his true enemy. After escaping, they encounter a dragon, a giant, and a werewolf before reaching Tarnberg, where the Saracen Carahue joins them. Following the advice of the wizard Martinus Trismegistus, they seek the sword Cortana, guarded by a nixie, cannibal hillmen, and a troll in a ruined church. During the quest, Carlsen and Alianora fall deeply in love, but he avoids consummating it, intending to return to the 20th century. Pursued by the Wild Hunt, they pledge their love, and Carlsen promises to stay with her if they survive. However, the decision is taken from him.

After recovering Cortana, Carlsen learns he is the legendary Ogier the Dane, a champion of Law. He defeats the forces of Chaos and is transported back to the battle at Elsinore, where he uses superhuman strength to vanquish the Nazis, allowing Bohr to escape and contribute to the Manhattan Project. In both worlds, Carlsen fulfills his destiny of fighting evil, but magic leaves him separated from Alianora. Desperate to return, he searches old books of magic, and his enduring connection to the medieval world is expressed by his decision to convert to Catholicism.