Picture a thunderstorm that almost never ends, producing up to 1.6 million lightning strikes a year and flashing 40 times a minute for nine hours a night. For centuries this everlasting storm over Venezuela's Lake Maracaibo was a permanent fixture of the planet, until January 2010, when the sky went terrifyingly dark.

This episode explores the Catatumbo lightning, the highest-density lightning on Earth, and the decades-long scientific quest to explain why it happens here. We trace the geography that traps the storm, the failed theories, the modern climate consensus, and the drought that briefly extinguished a phenomenon thought to be eternal.

• The atmospheric mixing bowl where warm Caribbean air slams into 12,000-foot mountain ranges and is forced violently upward
• The discarded theories, from Zavrotsky's 1991 uranium bedro ...