There is a battle playing out inside your body right now. It started billions of years ago and it is still being fought in every one of us every minute of every day. It is the story of a viral infection - the battle for the cell. This film reveals the exquisite machinery of the human cell system from within the inner world of the cell itself. From the frenetic membrane surface that acts as a security system for everything passing in and out of the cell, the dynamic highways that transport cargo across the cell, the remarkable turbines that power the whole cellular world, and the nucleus housing DNA. The virus intends to commandeer this system to one selfish end: to make more viruses. And they will stop at nothing to achieve their goal. David Tennant narrates.