We start the episode with a promise, a solemn vow. Rose Tyler is going to die. Awwwww yeah, about time.
Spooky ghosts are marching throughout the world. The Doctor gets out his proton pack and 3d specs, and traces the ghosts back to Torchwood, which is now based out of Canary Wharf tower. Fun fact, that's also where a madwoman overseeing experiments in space-time manipulation was based in the year 2006, in the book The Time Travellers, a first doctor adventure, did you know that? Just something to think about.
Right, so Martha's identical cousin starts slutting it up and gets killed for it, then becomes a cyberslut who lures upstanding homosexual men to their dooms. Turns out the ear doohickeys the Cybermen make you wear turn into cyber-brainworms. Oh, did I not mention it was the Cybermen? Yeah, it's the Cybermen. It's not much of a reveal, either. Really crummy.
Seems the Cybermen followed a big ole scary space sphere through the void between universes. That's other aliens, who get a proper reveal at the end, so I won't spoil it. Oh hell, it's only like a paragraph away, it's the Daleks.
So, people are getting Cyberconverted and the Cybermen are using Torchwood's big scary levers to suck Cybermen through from the other universe. And then they do, and they occupy earth in a single stroke. Then the scary space sphere in the basement opens up and, oh my god, it's the Daleks!
Did I mention Nicky came back? Because he's there too.
It's not bad. Pretty decent set up.