Somewhere in the middle of Epping Forrest in London, Derren Brown invites a New Age believer to a challenge where he will attempt to change her views and ultimately, her life by using a voodoo doll.
They sit on a fallen down tree and he begins to ask her about her beliefs about various things, crystal healing, spirituality etc.
Eventually, he starts to exercise the power of what a voodoo doll should do. Whilst with his back to her, he starts to bound the doll with twine around its base and at the same time, she feels that she cannot move her legs.
As with much of his work, he continually proves that the mind is very much over the matter - all the time. So with this in mind, anything is possible.