In The Cross, the last novel in the Kristin Lavransdatter trilogy, Kristin is living in a convent, helping nurse victims of the plague. Now about 50 years old, she has raised eight children who were fathered by her husband, Erlend Nikulausson. Although Kristin and Erlend were married despite her parents’ objections, they already begun a sexual relationship, and she was pregnant when they married. The marriage was rocky, in part because Erland’s service as a knight kept him away from home much of the time, and in part because Kristin was often impatient or harsh.

During one especially difficult period while her husband was living away from home, he paid a secret visit to Kristin and they had sexual relations. In those days, she was running their farm with a highly capable administrator, Ulf Haldorsson. Because the townspeople did not know about Erlend's visit, when Kristin became pregnant once more they assumed that Ulf was this child’s father and that she had been having an affair with the manager. This rumor led Erlend to a violent altercation with some of the rumor-mongers, which cost Erlend his life.

In the last days of her life, Kristin makes it her mission to save a boy whom the superstitious townspeople wanted to sacrifice, as well as to bury the boy’s dead mother. Ulf comes to the convent and helps her. Unfortunately Kristin is also afflicted, and passes away. Ulf not only knew her well from their time on the farm, but is further impressed by her selflessness in helping the critically ill. He tells the priest that he almost wishes that he had in fact had the sexual relationship with her that others had suspected.