Doctor Who Season 10 Episode 8
The Pyramid at the End of the World
Bill is enjoying a date when it's interrupted by the arrival of the Secretary-General of the United Nations, who is trying to get in touch with the Doctor.
The Doctor, Bill, and Nardole are called in to investigate when a mysterious ancient pyramid appears overnight in a contested region in the middle of three powerful armies belonging to the United States, China, and Russia.
It doesn't take long for the Doctor to discover that the pyramid was placed there by the mysterious and powerful alien Monks, who were running holographic experiments on how to conquer the Earth in the previous episode.
The Monks insist that the end of the world is at hand and that they will only save the world if they are asked and given consent out of love.
The Doctor eventually figures out that a disastrous lab accident is what the Monks are counting on to end the world. He goes to destroy the lab (and thus save the world) but gets trapped inside because he's blind.
Bill, the last one left standing in the pyramid, gives her consent to the Monks so that they will restore the Doctor's sight, allowing him to escape the lab before it explodes.