Brian Cox and comedian Robin Ince are joined by comedian Katy Brand and physicists Sean Carroll and Jim Al-khalili as they enter the strange and bizarre world of quantum mechanics. Schroedinger's famous thought experiment stuck a cat in a box and asked if it is dead or alive. Quantum physics says the cat is both dead and alive, until we open the box. This mind-bending idea may seem the realm of philosophy, but is actually the science that underpins most of modern life as we know it. Once the panel have dealt with the controversial issues surrounding cats in boxes, they explore whether quantum physics is really an accurate description of reality, and if it is, are there, as the theory suggests, infinite copies of you, me and everything in our universe all existing in every possible combination of ways of existing? If that is the strange but true reality of existence, will we ever be able to prove it?