According to her Wikipedia article, 15 year old Leonora Christina Christiansdatter af Slesvig og Holsten married 38 year old Corfitz Ulfeldt, son of the late Chancellor Jacob Ulfeldt, to whom she had been engaged since the age of nine. He held the lordships of Egeskov, Hirschholm Urup, Gradlitz and Hermanitz. In 1641 he was made a count (Reichsgraf) by the Holy Roman Emperor Ferdinand III. During most of the 1640s her husband's power and stature grew and she was, in many ways, the first lady of a Danish court that had no queen. Her marriage to Ulfeldt seems to have been a happy one. Her father, Christian IV, died in 1648. The new King, her half-brother Frederick III, and especially his Queen Sophie Amalie resented the Ulfeldts. The Ulfeldts went into exile.
When Ulfeldt was being sought for treason by the Danes, Leonora Christina went to England to solicit repayment from King Charles II of money her husband had loaned him during his exile. The King repaid his debt by welcoming his cousin the Countess to his table, then having her arrested as she boarded a ship to leave England, whereupon he turned her over to Denmark in 1663.
For the next twenty-two years she remained in the custody of the Danish state, incarcerated without charge or trial in Copenhagen Castle's infamous Blue Tower (Danish, Blåtårn). She lived under meagre and humiliating conditions for the daughter of a king, and was for years deprived of almost all comforts. During these years she perforce showed great stoicism and ingenuity. She wrote that her cell was small, filthy, foul, infested with fleas, and that the rats were so numerous and hungry that they ate her night candle as it burned. She learned to piece together pages for writing from the wrappers on the sugar that she was given, and to make ink for her fowl's quill by capturing the candle's smoke on a spoon. Slowly she adjusted to her plight, ceased longing for revenge or death, and developed a mordant humor. She studied the vermin who were her only companions, recording her observations and conjectures about their instincts. When she heard that her husband had died abroad, she marvelled that she felt only relief that he had finally eluded his persecutors.
During her imprisonment and for the twelve years she lived afterwards, she composed the book that made her famous, Jammers Minde (literally, "A Memory of Lament"), which was, however, only published in 1869. Now regarded as a classic of 17th century Danish literature, it explores her prison years in detailed and vivid prose, recounting her crises, confrontations, humiliations, self-discipline, growing religious faith and serenity, together with fascinating descriptions of hardships she endured or overcame.
She also wrote in French an account of her happy youth, La Lettre à Otto Sperling (Letter to Otto Sperling), completed in 1673 and smuggled out of the Tower. Seeking the inspiration to endure her ordeal, she had sought out and translated tales of women in adversity. Heltinders Pryd (Praise of Heroines), was penned in 1683 as a compilation of biographical sketches describing the different kinds of courage and endurance summoned by women whose struggles left an imprint on history. In the process she became something of a proto-feminist from the perspective of some later literary and political critics.
The saga of the prisoner of the Blue Tower — the fall of a mighty woman and her rise from despair to an even greater intellectual and spiritual might, as told against the backdrop of Europe during the Reformation — remains deeply compelling, even inspiring, as much to artists and the devout as to historians, patriots and feminists.