On the 25th of September 1996, the fifth class of the Master of Liberal Arts Program met in the History Building on the Main Quad at Stanford University. We were a disparate group; there was a physician, a librarian, a biology teacher and a few stay-at-home moms like myself, all eager to return to school as adults purely for the joy of learning. We ranged in age from mid-20s to the 70s, and many of us had not entered a classroom in decades.

The introductory class for the program was, for a number of years, "The Plague: An Introduction to Interdisciplinary Graduate Study," taught by Dr. Linda Paulson. While it might seem like a strange and unusual topic, the study of the plague (in many forms, places and eras) lent itself well to the theme of interdisciplinary study.

In addition to the many books written on the subject, the class syllabus also included guest speakers from a wide range of disciplines: medicine, literature, art history, theology and philosophy.

As we went around the room that night introducing ourselves, our nervousness was apparent, except for one person who could barely contain her enthusiasm. Her name was Ylva Hagner, in her early 40s with gorgeous red hair and blue eyes. Ylva was Swedish, lived in Palo Alto and worked at a software company in Belmont. She had a lilting laugh and was clearly enjoying herself.

In the third week of class, Ylva was absent. She had last been seen just before our class at her office. The weeks went by, and it was clear that something terrible had happened. Like many missing person cases, there was an initial flurry of interest in finding her that then lapsed into a cold case.

Our class moved on, with most of us finishing the program in four or five years. Ylva's disappearance cast a pall upon our Stanford experience, even though we got to spend so little time with her. Over the years, as we met at social gatherings or Continuing Studies classes, the question often arose — "How could someone just disappear without a trace?"

September 2021 marked 25 years since that first class, and I found myself thinking more and more about Ylva. Recent developments in DNA technology had brought closure to several highly publicized murder cases that had occurred near or on campus. Will we be around if, and when, Ylva's case is solved?

The Plague class brilliantly illustrated the many facets of a sweeping pandemic: We laughed at Boccaccio's characters, telling humorous tales to distract from the fear of illness, and the crazy bird-like masks worn by plague doctors (not realizing we would all, one day, be masked).

We were awed by the sheer numbers of people who died as The Black Death raged through Europe and how one type of plague was caused by the fleas on rats. We could not imagine people finding scapegoats to blame for a deadly virus or those who felt it was an angry retribution from God.

We learned all these things, in the abstract, from our readings and lectures — but the random, unfair and illogical specter of death was brought home to us, in reality, by Ylva Hagner.

Read more: 1996 cold case of missing Palo Alto woman resurfaces: Authorities search Redwood City property.

Sheryl Nonnenberg writes about visual arts for the Palo Alto Weekly.