At six years old, Bill Viola almost drowned: it is no coincidence that the greatest video artist of our days has developed his career through an incessant research centred on ridge between life and death. St Paul's Cathedral in London hosts two of his great artworks, one depicting the Madonna and the other four martyrs, one for each element: air, water, earth and fire. The story of their idea, construction, installation takes place over a ten-year journey of introspection and creativity for Bill along with his life and work partner Kira. The result is a set of universal and very moving images that make one reflect on birth, death, love, and sacrifice. Art that questions us about our role in the world.