Ultimum Mysterium attempts to explain mysterious phenomena from a new perspective. In Section I: "The Puzzle", the author sets out and examines a number of reportedly true cases of such activity, both from history and from more recent times, which are so bizarre that even current scientific theories are unable to offer an explanation. In Section II: "The Physics", the author reviews the latest scientific discoveries (mainly in physics, but also in neurological research) with a view to seeing whether these can offer any kind of explanation to the strange phenomena described in Section I. In Section III: "The Philosophy", the author examines the underlying philosophical issues to see what may be possible in terms of a scientific explanation. He argues the universe is what it is, regardless of what we may think about its workings. If the impossible happens, so be it. We need keep an open mind on the subject and embrace the bizarre, but fascinating world of the impossible.