Two bodies and one mind, this is the extraordinary story of one pair of conjoined twins in today's world.

Award-winning film-maker Antony Thomas examines the growing evidence that how twins turn out has more to do with their genetic make-up than their upbringing in this fascinating, moving documentary. The bitter feud between Tim Nicholas and his identical twin, Todd, was only resolved when Tim shot Todd through the heart. Identical twins, John and Bill Reiff eat together, sleep together, work together, and have known no other relationship throughout their adult lives. These are just two of the extraordinary personal stories that are uncovered during Thomas' journey through the private lives of twins; a journey that ends with a remarkable discovery.

Conjoined twins are among the rarest of human beings. There are probably fewer than a dozen adult pairs living in the world today. Only a few hundred pairs of conjoined twins are born in the whole world each year - they appear about once in every 100,000 births - but more than half of them are stillborn, and one in three live for only a few days.