Every action has consequences. Sometimes they’re good, sometimes bad, but when you travel with the Doctor, doing the wrong thing can be catastrophic. Rose is learning that the hard way.
All she’d wanted was to meet her dad; he’d died when she was a baby so she’d never had a chance to know him.
Instead, she saves his life and almost ends the world.
There are horrible red-eyed flying creatures. The Doctor calls them Reapers, says they’re sterilising the earth. They can’t be stopped…
…Unless what Rose did is undone.
Every action has consequences, and Pete’s death saves the world.