Many years ago Gwen Cooper joined Torchwood and was thrown into a world of terrifying danger.

During one of her first missions, the team visited Bute Park and witnessed a secret Government organisation, 'Unit Five', attacking a burning alien, eventually code-named the 'Dark Dragon'. Just before escaping, the burning screaming humanoid turned several teenagers inside out.

So Jack made a promise to Gwen - one day he would discover the truth about what happened that night.

The Miracle ended a month ago and Captain Jack has returned to Cardiff Bay...to take command of his new Torchwood team on Flat Holm Island.

Torchwood begins to investigate Unit Five, who are foolishly attempting to create a living link between a computer and Dark Dragon DNA. But something goes wrong, and the evil alien evolves, with terrible consequences for Captain Jack, Unit Five, Torchwood and the entire world.