The Doctor didn’t listen to Jack Harkness. She gave Ashad, the time-traveling Lone Cyberman, the Cyberium it wants to revive its own kind.
Now, she has to stop it before it kills the final humans.
Then someone familiar shows up, and is about to make things worse.
So why does the story also include an abandoned baby who lives a normal life, except for a few things?

SPOILERS BELOW

The episode is mostly about how Ashad (Patrick O’Kane) wants to lead the rebirth of the Cybermen. He’s managed to make two others, and has led battles to eliminate all but a few humans.
So how come the episode starts with the baby, who will be called Brendan and grow up in Ireland as a police officer? Two strange scenes may suggest a reason, but we’ll get to that later.

Most of the episode shows the Doctor and her crew trying their best to protect the last remaining humans, including Rovio (Julie Graham) and Ethan (Matt Carver), who is very good at hot-wiring spaceships.
They all hope to get to a place called the Boundary, an escape hatch where humans are taken to random places and away from the Cybermen. It’s guarded by a guy named Ko Sharmus (Ian McElhinney)
Ashad has been busy with a ship of his own, and even flying Cyber Heads. This is one of the scariest things in years.

Graham and Yaz join Rovio in a gravraft while the Doctor and Ryan manage to take over a Cyberman ship with Ethan. They’ll both get to Ko Sharmus, but it doesn’t mean they’ll get to safety.

The clash between the Doctor and Ashad is also very interesting. She tries to taunt him into thinking he’s more human than he thinks, and maybe loathes himself because he still half a face. Actually, he uses that to realize he was chosen to bring the Cybermen to glory. It’s a great scene, and adds a twist to the Cyberman history. He’s actually the most interesting adversary in this episode.

Yaz, Graham and Rovio arrive at a spaceship to speed up their journey to the Boundary. However, it’s a Cyber War Carrier with thousands of Warrior class soldiers familiar to those who remember them from the 80s. If they wake up, it’s bad news. That’s Ashad’s plan, and it’s not long before he does just that. Seeing him revive thousands of Cybermen may remind some of “Tomb of the Cybermen”, when a few dozen were revive. This is a much bigger deal.

The Doctor and Ryan do find Ko Sharmus, and he’s an Obi-Wan type of guy. He’s guided people through the boundary for years but decided to stay behind. It’s also been a long time since he’s seen any humans.
The Boundary is what looks like a beach, until a big purple portal appears.

Before we get to the final scenes, let’s get back to Brendan (Evan McCabe). During his career as a guard, he fell a hundred feet off a cliff while trying to stop an armed robber. Miraculously, he survived.
He had a long career, then was called in for a meeting just after his retirement. It turned out his memory was literally erased, but why?
Does it have a connection with the Cybermen?
Or maybe Brendan was a “timeless child”?
It’s really strange his adopted dad and his boss also haven’t aged that much, while Brendan is in his 60’s. Also, Brendan looks a little like Ko Sharmus.

Good questions, but there are pressing matters. Ashad has awakened thousands of Cyberman and are about to attack Graham, Rovio and Yaz.
Meanwhile, the Boundary reveals Gallifrey in ruins, and someone gets through.
Yes, the Master (Sacha Dhawan) is back, and he’s telling the Doctor everything is about to change. He’ll also explain why her life has been a lie.
OK, but what about the Cybermen? Unless the Master’s been helping them, it’s a little odd he’s chosen that time to arrive, even to torture her again.

This week’s episode was OK in showing the Doctor being very concerned about trying to save refugees and her friends from a Cyberman who’s close to reviving his kind. People may be confused about the Master coming back at that time, and then there’s Brendan. Hopefully the season finale next week can connect them all, and do it well.
Maybe someone else will be back, too.