It's the holy grail for limitless clean energy, but will nuclear fusion come soon enough to avoid the worst of the climate crisis? In France, Hannah Fry goes inside the largest international fusion project ever built and flies to Los Angeles to witness a new generation of private start-ups racing to put fusion energy on the grid.

The environment is in crisis, but a revolutionary new conservation concept offers hope for the future. From the overgrown Fukushima exclusion zone, to the majestic redwood forests of California, Hannah embarks on a journey into the wilderness to discover how championing nature could help to heal the environmental wounds we have inflicted on our planet.