I'm gonna go ahead and get this out of the way up front. This movie is silly.
It isn't a comedy, by any means. The characters (with what depth they have) are taken very seriously, and there is almost nothing in the way of situational humor. Civilisation has broken down all over Scotland, and the team is besieged by the results at every turn. The British government is corrupt, and the heroine is hard as nails.
What makes it entertaining is the degree of sheer ridiculousness the movie approaches with the material it uses. Doomsday is a post-apocalyptic grindhouse action-ride, and it throws so much at you that all you can do is laugh and stare and ask if it's kidding.
For starters, Eden Sinclair is essentially the daughter of Sarah Connor and Snake Plisskin who grew up next door to Richard B. Riddick. She wears a patch over her right eye while on missions, using her false eye as a remote-controlled, throwable surveillance camera that transmits to her watch, which functions as both a viewscreen and data recorder. She is precise and cold, existing for the job and only for the job, except for the rare moments she spends staring wistfully at the paper containing her Glasgow house address.
Her role in the movie is simple: find herself a bunch of ass and kick it to hell. She does this very well.
The virus is sort of a cross between the T-Virus, the Three Waters virus from the V for Vendetta movie, and the Black Plague. Its victims are essentially turned into tottering zombies without any craving for human flesh (and would you want to eat anything when your insides were being liquefied?) for the few hours before they die. Britain's decision to seal off the entire country of Scotland is amusing, but at least rationally executed, but at the gate during the evac, the guard who spotted the lone infectee predictably used forty bullets when one would have sufficed, and instead of dispatching the person off to one side he mowed them down right there in the middle of the crowd.
So right away you've got your blood and gore. Most of the deaths in the movie are high-blood-pressure spurters, and the virus fatalities spew all sorts of colored fluids and such from their mouths in the one or two scenes where they're shown.
Anyway, long exposition-laden movie segment short, Maj. Sinclair meets her team, is equipped with all the latest gizmos and gadgets and nice-looking FU-weapons and two smokin' tanks, and is sent trundling across the border with the admonition that if she can't find a cure she needn't bother coming back.
Incidentally, we're told that the Prime Minister is a puppet and his aide, who sounds like the descendant of a Scot and a German, is his puppeteer and the one who gave Sinclair her orders. Sort of a similar deal from Escape From New York except the evil government angle doesn't pop up nearly so often.
While the team is tanking through the Scottish countryside, they hit a cow.
A COW.
They have clear windshields and infrared front sensors and everything and still hit a cow. And it turns out that they're in the middle of a massive herd of cows. Small moment of humor, weirdly executed.
Once into the city, they drive around Uptown Glasgow looking for a hospital where one particular doctor had been working on a cure. They enter his lab without much issue, but just as they've found something possibly useful they're bum-rushed by the entire punk population of London and forced to retreat. They almost escape, but they lose both vehicles and three of the team to the barrage of bodies and molotovs-on-steroids (which can somehow penetrate a tank designed specifically to resist such methods). Two of the team members escape, but Sinclair and the team's scientist (haha) are captured and taken.
Turns out Glasgow is entirely populated by a huge anarchist-punk collective of cannibals, run by the slightly-insane be-mohawk'd Sol ("saul"), who personally interrogates Sinclair (where he gives her the diet Mike Tyson treatment) and immediately goes out to host and emcee the party where her captured teammate is barbecued and served.
This party is where the silliness really starts. A clear pit in front of the mob boasts a couple of guys pulling tricks on dirtbikes. There's some music blared while Sol goofs around on stage with a pair of poledancers, and the show immediately segues into the Can-Can, except the dancers now are portly bearded Scotsmen in wife-beaters and kilts. The barbecue car is a modified tow truck, with height elevations marked as Rare, Medium, and Krispy, complete with a tall, overweight chef.
Sinclair manages an adroit escape, in the process both rescuing the daughter of the scientist she's been sent to find and killing Sol's tattooed, sword-swinging girl. They flee the place, contact her two surviving teammates—her second and the other medic—and make for the train station, where waits a train to take them to Kane (the doctor).
Her teammates, meanwhile, have been intercepted by the punk maniacs, led by an enraged Sol driving an Attack Tour Bus. They manage to make it into the station, harried by guys on dirtbikes and punks on foot. One biker runs straight into a turnstile and lands badly on his head; both my father and I went "OOOOOHHH", and the trailing medic looked back and went "OOOOOHHH" and promptly tripped over his own feet. Sinclair belts another one in the face with a shovel, and they all escape—which, I admit, is a new one.
It's a new one for Sol, too. He gets so angry that he punches his own henchman hard enough to break the guy's neck.
It being a train ride, it's time for more exposition. Seems Cally (the rescued girl) is not only Kane's daughter, but Sol's sister. What a happy family.
That's about all we get before they're off the train in the middle of the countryside and into a bunker. Down, down, down they go, ending up in a storage facility with twelve-foot thick blast doors. An exit farther down leads them out into a forest, where they're met by Kane's "Executioner" who turns out to be . . . The Black Knight.
We left Kansas a while ago, guys.
Sinclair surrenders and is taken to Kane's castle. That's right. Castle. We have gone from Future Police-State to Post-Apocalyptic Punk to Medieval-Punk?
It gets better. Kane turns out to be Malcom Effing McDowell.
He's also insane. He reveals that there is no cure for the virus, and that the people living are merely the ones immune to it, but the quarantine of Scotland broke his mind, and he believes that the immunity was a "deliverance from sin". He locks everyone up, orders his daughter "cleansed" with a hot poker, and puts Sinclair in his courtyard coliseum, pitting her against the Black Knight.
While she wins, her team members (who are competent for a change) loose their bonds, overpower the guards, break into the armory where they find swords, spears, axes, bows and arrows, and—you guessed it—a grenade belt....
"Hey! This'll be handy." (actual quote)
...and then set about destroying the castle. They're hampered by all manner of armed occupants, including cooks (I guess that makes sense), and the medic starts to come into his own, busting people left and right with any improvised weapon he can find and earning a terse compliment from the sergeant.
The group flees the castle with Kane's men hot on their hooves. (Yay for stolen horses.) They dive back into the bunker, barricade (sort of) the entrance, and head back into the stockpile, ostensibly to equip themselves.
But Sinclair has other ideas. She wants to get out and to contact home. She finds the stockpile manifest on a handy wall and initiates a spot-search. And inside Cargo Crate #1 is . . . .
. . . a brand new Bentley. Keys hanging from the crate ceiling. Drums of petrol two aisles down. Why the hell not.
And from here on out it's basically just pure crazy entertainment. There's a nice chase scene, a mid-chase knock-down drag-out fist fight, Sol being more nuts than usual, some more random awesomeness from the medic dude, a few explosions, and the return of the Attack Bus. There is absolutely no reason for any of this, it's terrible plot, and somehow it's still managing to be awesome.
I'm not going to spoil the ending for you. Part of it's a little trite, part of it's lolworthy, and part of it's just a bit of what you sort of always wanted to see happen. And like I said earlier, it wasn't all that great of a movie from a story perspective. But given the choice between it and, say, Underworld or Hellboy?
Yes, Russell Crowe. I was entertained.