Dregs

"People can save planets, or wreck them. That's the choice. Be the best of humanity. Or..."

When the Doctor and friends arrived on Orphan 55, they found a devastated world where the biggest threat was that posed by the violent, deadly beasts known as Dregs. But in the process of escaping the dangers of this world, the Doctor discovered a horrible truth: for the Dregs are a future mutation of Humanity, reduced to slavering, bestial creatures as part of the effects of an ecological collapse. While the Doctor managed to get them away from danger, who can save Earth from becoming Orphan 55 in the first place?