So, we got a whole episode that barely had Donna in it. How about one that barely has the Doctor?
The Doctor and Donna are checking out some sort of future festival of some kind when Donna is lured away for a free palm reading. Then a large beetle attaches itself to her and changes her person history. And it’s such a small thing: due to her mother’s badgering, Donna makes a left turn instead of a right to go to some local job interview Sylvia Noble set up instead of the city temp job Donna already had.
As a result, Donna never met that man she almost married with the Rancross Empress and all her underground babies. Likewise, she never met the Doctor.
From there, life just stinks all over for Donna, her mother, and her grandpa Wilfred. Oh, and every so often, someone seems to see a large beetle on Donna’s back.
See, the Doctor still finds the Empress and takes her down…but this time he also drowns and doesn’t have time to regenerate because Donna isn’t there to snap him out of his fury. Now, the spider queen thing still doesn’t succeed, but things go worse from there.
When the Judoon steal a hospital to look for a suspect, there’s only one survivor, a classmate of Martha’s she gave the last oxygen bottle to. Sarah Jane had tried to save the day instead, but she and her kid friends all died there too.
The Doctor isn’t around to stop the Space Titanic from hitting London, leaving the Southern portion of the country a radioactive hellhole. Donna and her family were fortunately on holiday, but they are forced to relocate to a crowded house in Leeds.
America promises to bail Britain out, but then a large number of American die when a bunch of fat babies pop out of them.
Britain goes under martial law at one point.
Work camps for immigrants pop up. Donna’s grandpa recognizes what that means.
Torchwood manages to stop the Sontarans, but they all die as a result except for Captain Jack since he can’t. Instead, the Sontarans capture him.
And from time to time, Rose shows up to see if Donna is interested in fixing things.
The final straw is when Donna and Wilfred see the stars start to blink out of the sky one night. That…isn’t normal. And since the whole multiverse is threatened, Donna alone has to do something to fix history. That involves going with Rose, seeing the giant beetle, and stepping into the TARDIS to go back to that fateful day. She has to stop herself from making that left turn, and the only way to do that…is to step into traffic and kill herself, causing a delay in travel, and Donna went to London. Everything snaps back to the way it was.
The Doctor, for his part, doesn’t recognize the dead beetle Donna shows him, though apparently it took a lot of willpower to get everything back. Sounds like Sarah Jane’s pal the Trickster, but the thing is, Rose whispered something to the dying Donna, and the living Donna remembers it, and tells the Doctor two words: Bad Wolf.
And those words are everywhere.
That might mean the end of the universe.
That would be bad.