Three nuns vanished without a trace from the Convent of Santa María in Sigüenza on a cold February night in 1991.

The community searched for answers for years, but the case was shelved, becoming one of the great mysteries of rural Spain.

Thirty-two years later, during the renovation of the convent’s old library, a bricklayer discovered a diary hidden behind a false wall.

What those yellowed pages reveal not only solves the mystery of the missing sisters but also exposes a secret so dark that many in the small medieval town would prefer it remained buried forever.

The truth, hidden for more than three decades, will forever change our understanding of what really happened that winter night.

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Now let’s return to Sigüenza and discover how it all began.

A small medieval town in the province of Guadalajara.

It was then, as it is now, a place where time seemed to move more slowly.

With just over 5,000 inhabitants, its cobbled streets, the imposing Romanesque cathedral, and the limestone buildings created an atmosphere that seemed frozen in time.

The winter cold of the Castilian plateau penetrated to the bone, and heavy morning fogs frequently enveloped the town, giving it a mysterious air that contrasted with the warmth of its inhabitants.

The Convent of Santa María, founded in the 10th century, stood on the outskirts of the town, surrounded by fields of wheat and poppies that painted the landscape a deep red in spring.

The gray stone building, with its small bell tower and silent cloisters, housed a community of 15 nuns of the Discalced Carmelite order in 1991.

It was a place respected by the locals, known for its social work and for the delicious sweets the sisters prepared following centuries-old recipes.

The three nuns who disappeared that February night were very different from one another, though they shared an unwavering devotion.

Sister Lucía Martínez, 63, was the most senior.

A native of León, she had dedicated more than 40 years of her life to the order.

Firm but fair, she was responsible for discipline in the convent.

Her ever-vigilant blue eyes rarely missed any infraction of the rules.

Despite her apparent severity, she had a special talent for music and directed the choir with a passion that contrasted sharply with her usual reserve.

Sister Teresa Bch, a 42-year-old Catalan, had come to the convent after abandoning a promising career as a doctor in Barcelona.

Intelligent and pragmatic, she ran the convent infirmary and cared for the elderly members of the community.

Her face, framed by thin-rimmed glasses, reflected a serenity that was only disturbed when she spoke of her past, a subject she frequently avoided.

She wore a small silver medallion beneath her habit, the only material memento of her former life she had allowed herself to keep.

The youngest of the three, Sister María del Carmen Alonso, was barely 26 when she disappeared.

Originally from a small town in Extremadura, she had entered the convent only three years earlier.

After a personal crisis she never openly discussed, with her ever-present smile and contagious energy, she had quickly won the affection of the community.

She tended the garden and had a special gift for growing plants that others considered impossible in the harsh Castilian climate.

She kept a journal where she recorded not only the planting and harvesting cycles but also personal reflections on her spiritual journey.

The routine in the convent was predictable and orderly.

The day began before dawn with the recitation of Matins, followed by hours of work, prayer, and study.

Meals were simple but nutritious, and the silence was broken only during brief periods of recreation.

The three nuns shared this life of seclusion and service, seemingly content with their choice.

However, beneath this surface of conventual tranquility, subtle tensions existed.

In the months leading up to their disappearance, some residents of Sigüenza had noticed changes in the three nuns’ behavior.

Sister Lucía seemed more reserved than usual.

Sister Teresa had been seen consulting old archives in the municipal library, and the young María del Carmen had had several encounters with the local parish priest, Father Guillermo Sánchez—conversations that seemed to leave her visibly disturbed.

As the winter of 1991 advanced with its blanket of cold and early darkness, no one could have imagined that these three women.

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