Yksisarvinen (Finnish: The Unicorn) is a historical novel by Finnish author Kaari Utrio.
The general pattern follows Kaari Utrio's usual arrangement: a young woman and a young man encounter one another several times at different occasions. They are from very dissimilar backgrounds, but fate draws them together, and in the end they get each other.
Teenage twins Geir 'the Bear' and Ivar 'the Poet', sons of a Viking chieftain Inge Ragvaldson Jarl (Earl) and Ulvhild Svendsdotter, living in a Norse colony in Vinland, Newfoundland in America, started by Leif the Lucky, find a carcass of a whale, narwhal. They take its big horn-like tooth, tusk. The colony fares badly, and the family decides to emigrate to Scandinavia. After seeing the martyr death of their uncle, King Canute IV of Denmark, they end up in the area of Germany with their travel companions, a mission bishop and his family. The whale tooth - protected by a big bag - turns into a magical item of an unicorn, whose parts are believed to have magical powers. They get money of both letting people to touch the tusk, and of the amulets made out of it. Geir becomes Count Gero and marries Sigberta, the heiress of the Bishop's family's German county of Berga. Gero is restless and decides to embark to the First Crusade, after his young wife Sigberta has died leaving only a heiress, a baby-girl named Beatrix.
Meanwhile, in Italy, Juvalos Gerakis (Olaf Falco), by a Finnish mother and a Swedish father, born in Byzant, Count of Sinetra in Calabria and his second wife, Countess Aurelia (Aure), another Finno-Byzantine noble, rescue Aurelia's daughter Constantia - heiress of Montecaldo - from a bad marriage in Rome. They acquire a Roman fortified tower in the process and marry Constantia to Roger, (son of Count Juvalos by his first wife, the late Countess Adela), the heir of Sinetra. After this the Count sends his son and heir Roger to the Crusade. Constantia and her first husband, Knight Ferro Furni from Rome, had met a few years back Geir and Ivar in Hamburg and in Berga, when they were as envoys in Germany.
Count Geir, his brother Ivar and their retinue travel and have adventures with the Crusade. They meet the troops of Roger of Sinetra, travelling with his wife Constantia of Montecaldo. A love affair develops between Geir and Constantia. Part of the retinue gets abducted by Armenian mountain robbers, after a winter spent in Armeno-Cilician fortress they manage to flee. After Jerusalem is conquered by the Crusaders, Roger of Sinetra dies in the battle. The paramours now can have each other, and they get married. They embark on a voyage towards southern Italy with Constantia's young daughter Maria, who is the heiress of Count Juvalos of Sinetra. Maria's maternal uncle Arnulf,(son of Count Juvalos from his second marriage with Countess Aurelia), is the rival heir. Constantia has inherited the castle of Montecaldo from her father Fulbert.
The young Maria, is the great-granddaughter of Terhen of Arantila (Thorgerd, despoina Theodora Hyperborea, later Teodora de Meilhan) from the book "Vaskilintu", born in Finland, and the grand-daughter of Aure Nukuttaja of Launiala (di Bizancon, di Montecaldo, di Roccamorte, later Countess Aurelia of Sinetra), born in Finland. She is also the grand-daughter of the Italian-Norman Fulbert di Montecaldo and grand-daughter of the French-Norman Adela (de Meilhan), Countess of Sinetra. Her great-grandfather is the Swedish born Varangian Eirik Väkevä. People believe that Maria's two ancestresses, Terhen 'Theodora' and Aure 'Aurelia', were Byzantine noblewomen. In the twist of the plot, 'Byzantine' is a code word disguising the Finnish background. Her great-grandfather spatharokandidatos Eirik Väkevä and great-uncle droungarios Leo (Lyy Judge of Launiala, born in Finland) were army officers in the service of the Emperor of Byzantine in Constantinople, in Varangian guard. Maria's parents Constantia and Roger were both born in Italy.