The whole world wakes up to find that it’s been turned into a forest. The Doctor must figure out how and why, and a little girl may be his only hope. It’s a cute fairy tale for the show before the grim season finale.

This used to be real estate
Now it’s only fields and trees
Where, where is the town?
Now, it’s nothin’ but flowers

–Talking Heads

That is what the world has become, apparently, overnight. A little girl named Maebh Arden (Abigail Eames) is running, apparently looking for the Doctor, because she just thought of it. He lets her in to the TARDIS, but is puzzled that he didn’t land in the middle of London like he planned. Actually, he has, but he wasn’t seeing the forest for the trees.

Maebh is actually part of Coal Hill’s eighth grade “gifted and talented” class, and they had a sleepover at the British Zoological Museum with Danny Pink (Samuel Anderson) and Clara. They soon see the trees, too. Clara calls the Doctor, who tells her about Maebh. Danny asks if she was calling the kids’ parents, and pretends that she did. They clearly have different priorities, but he has a point. The kids see them argue, and they figure they’re in love.

Seeing the Doctor and Maebh try to make sense of the situation is kind of cute, especially when she claims the trees all communicate with each other, while he says there’s no “tree Facebook”.

Yet Maebh seems to be the key. A pile of her homework books is somehow in the TARDIS, and one of them show a massive solar flare headed straight for Earth. Clara says that can’t be possible. Maebh has been traumatized ever since her sister Annabel disappeared last year. She even claims she hears voices.

Meanwhile, the kids wonder why Mr. Pink doesn’t work harder to help Clara out, since they think they’re a couple. It’s true, but the kids are too perceptive about that.  They also realize the trees may have broken the barriers at the zoo, which means the animals are running around loose. They hear wolves howling, but the wolves don’t attack because they’re too worried about the tiger behind them. Thanks to Danny’s flashlight, the tiger is driven away.

Maebh is soon directed to the center of the forest, which is a bright ring. She is flailing her arms, trying to catch the “thoughts” only she can hear. With the help of the Sonic Screwdriver, they all see mysterious fireflies that identify themselves as “the life that prevails”. It claims the sun had called them.

It looks like the Earth is doomed, The Doctor thinks he could save the kids, or at least her. Clara says not a chance. She doesn’t want to be the last of her kind, and Danny will never desert the kids. He finally admits that Earth is his world, too, but Clara says that this time, the humans will save him. She wants him to go.

He does leave…only to figure out that Earth may not be in trouble after all. The flame-proof trees are there, he theorizes, to protect the planet from the solar flare. It happened before when massive meteorites hit Tunguska, Russia in 1908 and Curuca, Brazil in 1930. The trees were also there to mitigate the damage. That’s why the Earth literally went green, because it “knew” the trees could ward off the flare.

One problem: government officials are about to defoliate the trees. The Doctor’s idea: call everyone on Earth and tell them to leave the trees alone. Maebh volunteers to make the call, since she thinks she made the trees grow. The call works, and the trees do protect the world from the flare. While everyone is happy, someone is not. Missy (Michelle Gomez) sees the Earth survive, and says it’s a surprise, and she likes surprises the same way Boston likes the Yankees.

Clara invites the kids to see the trees save the Earth, but they’d rather go home. Same for Danny, who says the situation made him appreciate what he almost lost while he was a soldier. He also insists Clara be more honest with him about her urge to travel with the Doctor.

So what happens after the forest is gone? The Doctor says people will just forget, since that is mankind’s super power. If they didn’t forget, they’d stop having wars…and making babies.

Maebh is reunited with her mother, and later with her missing sister. She says she had a feeling Annabel would be there.

The episode was more like a fairy tale more than science fiction. It had an enchanted forest, magical sprites, a dashing hero, and a happy ending. It also shows Danny’s more serious in his job as a teacher than Clara. That only makes sense if you remember how flighty she was with Eleven. If she does stick with Danny, she’ll get more serious, too.

Next week, though, marks the start of the season finale, where Clara betrays the Doctor, UNIT is threatened by Cybermen, and Missy’s real identity…and maybe Clara’s..is finally revealed.