The Village That Dreamed Itself to Death - S1.E5

The children respond to a distress call from Loppergarth Island. When they arrive, they find Loppergarth Island deserted, save for Gemma, a sleep-deprived young girl in shock after a week of compulsively trying to stay awake. They eventually ascertain that her parents and the rest of the populace have been consuming contaminated gull eggs, causing them to fall under a shared hallucination and gather to become comatose in the village church for an otherworldly crystal entity.