The Doctor is still pondering the Monk's final words when a voice is heard.
"Doctor! Help us! We need help, Doctor!"
On its own, the TARDIS takes flight to the point of the distress call: New Earth.
Cue Title Sequence: Plan Z
Almost immediately, the Doctor experiences what's wrong when a violent earthquake happens as he steps out of the TARDIS. This earthquake causes one of the distant buildings to collapse, screams filling the air. Cracks form around the Doctor, and he eventually falls through the ground. Something catches him in midair, something akin to a giant gust of wind accompanied by a near deafening roar. The Doctor eventually lands, knocking over several people calling out for the Doctor.
"Who are you?"
"I'm the Doctor."
"You can't be the Doctor, you're shorter, younger...pudgier."
"OI!"
After some back and forth insults and a "What the hell is going on?!" later, the answer comes in the form of another near deafening roar and a massive tremor followed by the cavern being covered in a red glow.
"What's wrong, is the center of the Earth inhabiting giant spiders again?"
"It's not the core, boy, it's the whole planet!"
For the first time in the past hour, he is surprised. The planet itself was alive.
"Wow...I've seen it all. Now I've truly seen it all. Forget parallel dimensions, forget the parasitic sun, forget the moon egg, forget the Timeless Child...never before have I ever, in my twenty-five hundred years of existence that I actually remember, seen a habitable planet itself be the monster."
PLAN: There is no plan. For now.
QUESTION: Why now? Why is the planet becoming active now?
ANSWER: It's finally waking up.
It would take a lot longer for the Doctor to realize this and for the Doctor to come with
THE SOLUTION: Sing it a lullaby.
Being shy about his singing, the Doctor opts for one of the people stuck there (who, for convenience, is named Derek) to sing instead. Derek doesn't even get to the second note before the planet roars and heats the air around Derek to melt his skin off. Bucking up, the Doctor steps up and begins to sing. Things start to heat up, but instead of screaming in terror like Derek, the Doctor continues to sing. Tremors start to happen at a rapid rate, but the Doctor continues to sing. Wind picks the Doctor up, but he still continues to sing. Finally, the tremors stop and the glow is gone. The planet has fallen asleep.
"If I know anything, this will continue to happen. Every two years, I'd say. When it happens, find the point where the tremors are the most dire, and sing. If you don't want to cause panic...well you can always bring back the Olympics."
With that, the Doctor says goodbye and goes back to the TARDIS, humming the lullaby he just sang.
Roll Credits: The Doctor Will Return in - The Body of Carrie