All Flesh is Grass

Even a Time Lord can't change the past.
A wasteland. A dead world. No, there is a biodome, rising from the ash. Here, life teems and flourishes, with strange and lush plants, and many-winged insects with bright carapaces - and one solitary sentient creature, who spends its days watering the plants, talking to the insects, and tending this lonely garden. This is Inyit, the Last of the Kotturuh.
In All Flesh is Grass we are transported back to The Dark Times. The Tenth Doctor has sworn to stop the Kotturuh, ending Death and bringing Life to the universe. But his plan is unravelling - instead of bringing Life, nothing has changed and all around him people are dying. Death is everywhere. Now he must confront his former selves - one in league with their greatest nemesis and the other manning a ship of the undead.