The Earth is being overwhelmed by huge trees that have popped up all over the world over night.
A little girl runs to the TARDIS in search of The Doctor. She thinks that Miss Oswald asked her to find The Doctor, but now it might only be in her head.
The Doctor doesn't understand how they can be in the middle of London, which is also a forest.
Danny and Clara had some students on a school trip sleepover at the local museum. They cannot open the museum doors because they are barred by trees.
Danny is angry that Clara is in contact with The Doctor. She then wonders where Maebh might be. Aha! Danny has lost her and she's with The Doctor.
The kids are so logical. If the trees came overnight then why can't they go as quickly? Even in lessons, "How do you find X," Ruby tells Danny it's not missing. It's right on top.
Maebh hears voices and takes tablets and they stop. The Doctor realizes she's tuned into a different channel.
Maebh is leaving a trail for Clara to find. She runs across the men in suits who are burning the forest. Clara and The Doctor find it as well.
Maebh communicates with the life that has been here long before The Doctor. Essentially, the regrowth is going to happen whether they like it or not.
Clara doesn't want to be the last of her people so she sends The Doctor away from the planet they both love.
Inside the TARDIS the solar flare is coming and the forest will protect everyone because it's a flameproof forest.
Danny wants Clara to go home and think about things before she decides to tell him whatever she wants to tell him. She is surprised he doesn't want to see the solar flare up close. It's just not his thing.
Clara goes with The Doctor to watch the flare, the children return home safely, the trees protect the earth.