It begins with a phone call. Stage 4 Hodgkin's Lymphoma. Seventy percent chance of survival. The author's younger brother, calling on the night before a mountain bike race. That call ended a career spent chasing trophies and began something more serious — a decades-long pursuit of a system for living at full capacity, for as long as possible.

The sauna and the cold plunge are at the centre of that system. This book explains why, and exactly how to use them. The science is peer-reviewed. The protocol is specific. The history spans every civilisation that ever survived a hard world.

Hot and cold therapy is at the core of living to a hundred. The repeated cycle of thermal stress and cold exposure triggers the body's deepest repair mechanisms — heat shock proteins that protect and rebuild cells, cold-activated norepinephrine that sharpens the mind and burns dormant fat, and a cardiovascular workout that rivals distance running without a single step. Every civilisation that produced centenarians understood this. The Finnish, the Japanese, the Romans, the Scandinavians — they all built rooms of heat. The science now confirms what they knew by instinct: the forge of hot and cold is the closest thing we have to a longevity protocol that costs almost nothing and works for almost everyone.

With tales from the north — true modern viking stories from today — woven throughout, including guest chapters by Erik's sister Kajsa and his brother Anders, who rebuilt his life after cancer around three principles: a sauna always warm, a table big enough for everyone, and food with a story.