In May 1919, the thirty-seven-year-old Norwegian author Sigrid Undset was at a crossroads. Her family had just been evicted from their apartment in Kristiania (now Oslo), and although her husband, the painter Anders Castus Svarstad, had promised to purchase a house for the family, he had not done it in time. Two babies and three teenage stepchildren, without a stable shelter – and as usual, the responsibility for the blended family fell entirely on her shoulders. After seven years of marriage, she could no longer deceive herself that Svarstad’s chronic evasion of responsibility was a high-minded indication of artistic temperament. She knew now that if her health failed, Svarstad would dump her children in an orphanage, just as he had done at first with his older children when he divorced their mother to marry her. And she was pregnant again.

The strain wore on Undset as she struggled to keep her own literary career afloat, writing essays and translating literature late into the night. Then, at least, she was free from managing both infants and her teenage stepdaughters, juggling finances and housekeeping, worrying about her baby’s epileptic fits and her stepson’s mental delays, and reckoning the emotional toll of marriage to a man whose aloof preoccupation had once been her romantic ideal. Before her marriage she had been Norway’s most celebrated woman author, acclaimed for Fru Marta Oulie and Jenny, both “scandalous” tales of modern women breaking taboos; and Gunnar’s Daughter, a short historical novel in the style of her beloved sagas. She had attempted, on and off through these past years, to write an even more ambitious saga, a rich evocation of the world of medieval Norway that her archeologist father had brought to life for her. Now she had no home to write in, and, for all intents and purposes, no husband.

Three years later, Undset would astound the world with the publication of the epic saga Kristin Lavransdatter, composed in a burst of creative energy in the house she bought herself. The writing of her masterpiece, at once an effortless immersion into its historical period and a keen account of moral choices played out and compounded over time, marked a turning point in Undset’s life, crystallizing her decision to convert to Catholicism in 1924, and winning her the Nobel Prize in Literature in 1928. Although her childhood and education gave her a unique advantage in bringing fourteenth-century Norway to life for a modern audience, it was her own complicated relationship with Svarstad that provided the model for Kristin and Erlend’s passionate, scorched-earth relationship, and her own spiritual yearnings that found voice in Kristin’s prayers.

Kristin Lavransdatter remains one of those books that burrows its way into your consciousness and never quite leaves you alone. For one hundred years readers have been enthralled, and at times enraged, by Kristin, a sensitive, headstrong beauty with a singular talent for choosing the complicated path. The three volumes – The Wreath, The Wife, and The Cross – trace her life over a sweep of four decades, charging along, after a gentle childhood introduction, over one thousand pages of love, lust, and spiraling consequences in fourteenth-century Norway, where institutional Christianity has not entirely loosened the hold of the ancient pagan traditions. In her relationships, both human and divine, Kristin seeks forgiveness for her trespasses without having to forgive anyone herself. But in the finest tradition of the sagas, small incidents can escalate on short notice, with life-altering (or -ending) consequences. And Kristin comes to understand, often the hard way, that God’s mercy must be accepted with open hands, not bought with pious rigor or pagan rituals.

The first novel, translated in English as The Bridal Wreath, opens on a world of family ties and constraints. Kristin’s beloved father, Lavrans, an esteemed landowner in the Gudbrandsdal valley in Central Norway, is an intensely pious man, but still treads warily beyond the boundaries of the sparse Christian settlements of the mountains and valleys, where ancient spirits still might retain their power. Her mother, Ragnfrid, is a capable mistress of her estate, but grief over early losses checks her relationship with both Lavrans and Kristin. Through her parents’ courteous but distant marriage, young Kristin learns early to be secretive, letting intense emotion simmer within her.

At age seventeen, Kristin is placidly engaged to the honorable, steady Simon Andressøn, her father’s choice. After a local tragedy threatens her reputation, her parents decide she will be safer in a convent school in town for a year. It is in town, however, that she is swept off her feet by a chance encounter with the older (not wiser) Erlend Nikulaussøn. Erlend is graceful, romantic, guileless, and has an almost childlike inability to understand how his reckless past can have any bearing on his future. Despite Kristin’s engagement, the pair vow they will be married to no one else – a vow neither of them is truly free to make, though Kristin is not yet aware of the extent of Erlend’s entanglements. Only afterward does she learn, and not from Erlend himself, that he has two illegitimate children with another man’s wife. Even this does not deter her.

Kristin imagines, with willful naïveté, that she can conceal any consequences from Erlend’s increasingly indiscreet seduction. She tramples on both Simon and her father, who struggle at the cost of their own humiliation to guard her reputation. Surely every betrayal will be rectified once she and Erlend have the full social and religious standing of marriage. But Kristin is pregnant by the time her lavish wedding ceremony finally takes place, and she wears the maiden’s bridal wreath with a sick unease at the farce to which she has made her good parents an unwitting party. This deception coats her soul with an acid layer of guilt which no subsequent penance seems able to dissolve.

Sigrid Undset, born on May 20, 1882, was the oldest of three sisters, brought up in the midst of their father’s academic career and research. Her mother, Charlotte, though somewhat imperious, was intelligent and active, collaborating with her husband, the eminent archeologist Ingvald Undset, on expeditions and in his scholarly work. Sigrid’s immersion in historical detail began early in life. Ingvald, recognizing the potential of his intelligent, sensitive, reserved daughter, taught her Old Norse and regaled her with tales of the great king Saint Olav who brought Christianity to Norway. The past was as vivid as the present to young Sigrid: her favorite toy was a terra cotta horse from the thrilling excavations at Troy, a gift to the family from famed archeologist Heinrich Schliemann himself.

Though Ingvald and Charlotte Undset were nominally Lutherans, they raised their children in a secular milieu. Undset attended a progressive co-ed school that prepared women for the liberal arts exam required for university admission. Her father wanted her to carry on his work, and talked politics and history with her as if she were an adult. But this idyllic childhood was overshadowed by Ingvald Undset’s failing health, the lingering effect of malaria he contracted two years before Sigrid was born. As she sat by his bedside during his final illness, eleven-year-old Sigrid read to him from a book her grandfather had recently recommended to her, a literary revelation she remembered as “the most important turning point in my life”: Njál’s Saga, the great Icelandic tale of family feud, honor, and fate.

Sigrid dreamed of writing her own epic, but Ingvald’s death meant that the family could not afford further schooling and at sixteen she had to leave school to work. For ten dull years she worked during the day as a secretary for a large firm, but in her spare time she wrote, gathering material and making outlines for a lofty historical novel about an unhappy marriage. Her ambition outstripped her experience: when she submitted her manuscript to a publisher, he gently advised her to set aside the historical project and start with “something modern.” Stung, Undset sat down and dashed off an opening line: “I have been unfaithful to my husband.” “That, I felt, should be modern enough,” she wrote of her 1907 novel about adultery, Fru Marta Oulie. As is so often the case with novels designed to shock, it achieved its end. The popular reception of this book paved the way for the kind of book Undset really wanted to write, Gunnar’s Daughter, a saga of rape and revenge which established her literary reputation. After receiving an artistic grant from the government, she quit her job and traveled throughout Europe. In Rome, at a boarding house for Norwegian artists, she met Anders Castus Svarstad on Christmas Day, 1909, and the course of her life altered.

In The Wife, (originally translated in English as The Mistress of Husaby) Kristin struggles to understand how to live in a marriage that is nothing like the gentle model of family life she knew growing up. Erlend has always intended to be a good husband, and for a while he tries to aid Kristin as she restores his neglected estate to its former prominence. Kristin has a gift for this kind of management. But it is not the kind of life that suits Erlend. He does not have the strength of character to settle down to the mundane accountability of family life, or to bear his share of the pain that he causes her, whether the physical agony of pregnancy and childbirth, or her building resentment that he does not feel the same guilt she does for their sins. It is difficult to wield authority over children or servants when that authority involves enforcing the social norms and ties that she and Erlend so flagrantly flaunted in the beginning. Kristin neither forgives nor forgets, and Erlend neither remembers nor repairs. But Erlend has a magnetic ability to repel and to attract. When he gambles everything on a risky political intrigue, Kristin clings passionately to him, oblivious to the strain she is putting on her children and her friendship with the loyal Simon, now her brother-in-law.

Anders Castus Svarstad was a painter – romantic, brooding, and thirteen years older than Sigrid Undset. As a nineteen-year-old working girl, she had once bought one of his paintings. Now, at twenty-seven, she fell desperately in love with the man himself. “I think I need to lie down and kiss the ground in all humility – I think I need to serve every living thing – because I am happier than I ever knew a person could be,” she wrote to a friend – the exact sentiments the inexperienced Kristin would express after her first meeting with Erlend, ten years her senior.

It’s possible that Undset knew from the start that Svarstad was a married man; his wife, Ragna Moe, had been a classmate of hers. While Undset the nineteen-year-old secretary was buying her painting, Moe was starting a relationship with then thirty-two-year-old Svarstad. Their first child was born in 1903; they were married a year later. The marriage seems to have floundered from the beginning; he spent most of his time away from his family, traveling in Europe, and wasn’t even certain that the youngest child, a one-year-old boy, was his. Now, as Undset traveled back to Norway in 1910, Svarstad met her secretly in Paris. He had decided to go home as well, to start divorce proceedings. Since the children’s mother would be unable to care for them on her own, Svarstad made plans to send them to an orphanage.

While she waited for Svarstad to free himself, Undset wrote Jenny (1911), about a Norwegian artist who finds love in Rome. It was an ominous story for a woman who had so recently found love in Rome to write: the early happiness of the relationship descends into a lurid series of almost inevitable tragedies, culminating in the death of Jenny’s illegitimate child and her suicide. The novel, however, was a scandal and a success throughout Europe, proclaimed shocking and winning Undset feminist accolades. She set small store by this kind of notoriety. Undset would always have an uneasy relationship with feminism, which she felt reduced the irrefutable biological connection of mother and child to a mere political position, and catered to middle-class women at the expense of the poor. “The weakness of the movement,” she later wrote, “was that from the very beginning it had a tendency to keep an account only of its gains and not of its losses.” As her marriage approached, the thought of motherhood, and the fate of children conceived out of wedlock, consumed her. By her wedding day in June 1912, Undset was already two months pregnant.

In The Cross, Kristin and Erlend, who have never been able to fathom the damage their self-absorption has wrought on others, are finally reaping what they have sown. When Erlend’s recklessness finally costs him his position and his property, the family is forced to move from Erlend’s grand estate to Kristin’s girlhood farm. Now, as Kristin scrapes a living for the family with no practical assistance from Erlend, his every action rubs her battered heart raw. Still, after a separation, one last burst of the old passion shakes their tempestuous marriage to its unstable foundations, catching everything and everyone in the aftershock.

Her faith has always been a source both of strength and of torment to Kristin, who does all things well except letting go of what she loves. As her earthly attachments, one by one, lose their allure, she begins to see that God’s love cannot be reduced to the pagan tit-for-tat of sacrifice, or the fervor of emotional experience. After a lifetime spent in bitter regret for one thing after another, Kristin realizes at last that when she comes to God, she will bring with her only the good deeds of her life, which flow from God and must return to him, the source of all goodness. And the good that we do in life cannot be taken back, because God’s good is eternal.

After seven years of marriage, worn by the horrors of the Great War and the increasing strife in her own household, Sigrid Undset realized that if her family was to be provided for, she would have to do the providing. Anders Castus Svarstad had proved no more effective a husband to his second wife than to his first. He felt hemmed in by his growing family and his waning influence on the Norwegian artistic scene. He wrote screeds about the dangers posed by the Prussians, the Bolsheviks, and the Jews. The difficulties of caring for his own disabled children had driven yet another wedge between him and Undset, who had developed a deep compassion for the “flotsam” of the world. In May 1919 she took a year’s lease on a timbered farmhouse on the outskirts of Lillehammer. It was at this farmhouse, later named Bjerkebæk, that she began intensive work on her epic, set in the same Gudbrandsdal Valley she could see out her window as she sat at her desk chain-smoking. She prepared a studio for Svarstad, but he did not choose to live with his family again.

Freed from the emotional toll of being dependent on Svarstad, Undset blossomed both personally and artistically. Kristin Lavransdatter flowed from her pen at a furious pace – a novel a year from 1920 to 1922. Writing three international best sellers in a row, combined with an annual artistic stipend from the Norwegian government, brought the forty-year-old Undset a level of financial security she had not known since her father was alive, and allowed her to make real provision for her disabled daughter. Although she had hoped for a reconciliation with Svarstad, the decisive break came in late 1920, as Undset was working on The Wife. That book, when it was published, would be dedicated to her ideal of a husband: her father.

Ingvald Undset had shaped his daughter’s imagination with stories of the patron saint of Norway, the Catholic king Saint Olav. As Undset researched the world of Kristin Lavransdatter, it was Saint Olav’s pre-Reformation Catholicism she studied. She was fascinated, then attracted, then convinced. In 1924, after petitioning for a divorce to formally dissolve her relationship with Svarstad (a relationship the Catholic Church did not recognize since he was already a married man) Sigrid became an active member of Norway’s tiny Catholic community. For the rest of her life, she would write in sometimes too-spirited defense of her religion, becoming known as the “Catholic Lady” by scornful Lutheran critics. Unfortunately, as is so often the case, her convert’s zeal took its toll on those closest to her. Although Undset’s oldest stepdaughter and her mother also became Catholic, her son Anders, most like his father, ended up professing no religion at all in his teenage years. Hans, only five when his mother converted, developed a conflicted relationship with both Catholicism and his mother after being sent away to Catholic boarding school.

In 1928 Undset was awarded the Nobel Prize in Literature, which brought her to the attention of the world. Her fame would come at great personal cost. Undset’s outspoken condemnation of Nazism made her a high-profile target when Germany invaded Norway in 1940. She fled with Hans to the United States, where for five years she worked tirelessly for Norway’s liberation. In 1945, she returned home, but she was weakened by grief for Bjerkebæk, left in shambles by Nazi occupation, and for her lost children: Charlotte, who died in 1939, and Anders, killed in action just days after Undset’s escape. Her once indomitable creative spirit was shattered. Hans, always in financial difficulties, pushed her to accept a problematic American film treatment of Kristin Lavransdatter, but their deeply-rooted tension had a different source. In a dramatic scene worthy of Kristin and Erlend, mother and son came to high words and a bitter parting over his homosexuality. To Hans’s lasting grief, they would never be reconciled; Undset went into a sudden decline and died unexpectedly of a kidney ailment on June 10, 1949.

Over the years, most of Undset’s works have fallen by the wayside, deemed too polemical or too of-the-moment. The Kristin Lavransdatter trilogy, however, transcends the one hundred years since its publication – and the seven hundred years between Undset and her characters. Undset’s grounding in Norway’s past made Kristin Lavransdatter a masterpiece of national and world literature, but her keen moral realism and understanding of the human heart sprang from her own history: the humbling failure of her own marriage, and the spiritual quest for eternal truth inspired by research into the faith of the past.