Becoming a father is an extraordinary adventure in a man's life, but it is also a real physiological metamorphosis that science is only just beginning to reveal. Researchers from multiple disciplines are lifting the veil on these changes taking place in men who are in contact with young children, and their discoveries are astonishing. By tracing the thread of evolution, the film reveals that these deep, long-ignored bonds between men and children are very ancient. And that they are just waiting for the right context to fully express themselves.