In the mid-1940s, the town of Mattoon, Illinois, was gripped by reports of a mysterious gasser who appeared to attack people in their homes. Over about two weeks, more than two dozen cases were reported to police, with victims describing strange odours followed by paralysis in the legs, coughing, nausea and vomiting. No one died or suffered lasting harm. Police stayed sceptical, and many incidents had ordinary explanations such as spilled nail polish or smells from animals and nearby factories. Local newspapers ran alarmist stories that treated the reports as fact, which fed further sightings. Most historians now see the episode as mass hysteria, though some people still believe a real gasser was involved.

Hampi is a UNESCO World Heritage Site in Karnataka, India, with more than 1,600 surviving remains spread over 4,100 hectares. It was the capital of the Vijayanagara Empire from 1336 to 1565. Travellers from Persia and Portugal described it as a prosperous, wealthy and grand city with temples, markets and farms along the Tungabhadra River. By 1500 it was estimated to be the world's second-largest city after Beijing, and probably India's richest at the time. In 1565 a coalition of Muslim sultanates defeated the Vijayanagara Empire, its capital was conquered and destroyed, and the city was left in ruins. Hampi remains a religious centre, with the active Virupaksha Temple at its heart.