In this episode, Michael meets tremors-sufferer Thomas who is about to undergo pioneering brain surgery, and Allen, who finds out if his experimental cancer treatment has been a success.

The presenter heads to Snowdonia, on a mission to demonstrate what stress does inside all our bodies, and in Durham, cameras reveal that we all possess an incredible hidden ability. Plus, a woman explains how she learned to see again by using echolocation.

The presenter meets a community group in Glasgow, and reveals the best way to keep our brains young as we age. At Royal Papworth Hospital, cameras follow a life-saving procedure to treat Clifford, who has developed dangerous blood clots in his lungs. And a woman shares the secret of how she is long-distance running well into her seventies.