When Mike's knee trouble starts getting in the way of The Unexplainers' research, the team set out in search of the best healing powers in Wales.

Routine research into a boy with ball of fire for a face reveals that Mike needs some deep healing. Fellow Unexplainer John realises that there's only one thing worse than having a skeptic on the team, and that's having a skeptic with knee trouble on the team. To help Mike repair his formerly sportsmanlike body, John begins a quest to rid him of his ailments and keep him alive.

John isn't satisfied by the workings of modern medicine and instead opts for tracking down the healing power of the Holy Grail in a Welsh manor house. But when the cup of Christ doesn't yield instant results the duo begin an epic quest for alternative therapies. The final experiment not only blows John's mind, but changes everything for Mike too.