TURMAKHAND, Nepal — Not long ago, in rural western Nepal, Gauri Kumari Bayak was the spark of her village. Her strong voice echoed across the fields as she husked corn. When she walked down the road at a brisk clip, off to lead classes on birth control, many admired her self-confidence.

But last January, Ms. Bayak’s lifeless body was carried up the hill, a stream of mourners bawling behind her. Her remains were burned, her dresses given away. The little hut where she was pressured to sequester herself during her menstrual period — and where she died — was smashed apart, erasing the last mark of another young life lost to a deadly superstition.

“I still can’t believe she’s not alive,” said Dambar Budha, her father-in-law, full of regret, sitting on a rock, staring off into the hills.

In this corner of Nepal, deep in the Himalayas, women are banished from their homes every month when they get their period. They are considered polluted, even toxic, and an oppressive regime has evolved around this taboo, including the construction of a separate hut for menstruating women to sleep in. Some of the spaces are as tiny as a closet, walls made of mud or rock, basically menstruation foxholes. Ms. Bayak died from smoke inhalation in hers as she tried to keep warm by a small fire in the bitter Himalayan winter.