You're probably a little bit lost by now, plus you're probably getting the Underworld and Resident Evil mythologies mixed up by now, so here's a quick recap:
1. Underworld (2003) -- It's the Monatgues and the Capulets all over again, only this time they're warring families of vampires and werewolves.
2. Underworld: Evolution (2006) -- Just a continuation of the earlier stuff, with Selene and her "Lycan Hydbrid" hubby trying to stay alive while trying to figure out some boring old mysteries.
3. Underworld: Rise of the Lycans (2009) -- Ms. Beckinsale took most of this movie off, which might explain why it was a meandering prequel starring an actress who looks a lot like Kate Beckinsale.
4. Underworld Awakening (2012) -- Easily the best of the three sequels (sue me, I like the first movie), which isn't saying a whole lot, but it's important to judge every film (even a Part 4) on its own merits (or lack thereof), and it's also important to take notice when the producers of a popular series pay attention to the complaints that the fans have voiced throughout the series. This is not to say that Underworld Awakening is not an editorial mess (boy, is it ever), nor is that to say that Underworld Awakening has a smooth and sensible screenplay (it's a sloppy concoction, and that's me being nice) -- but Underworld Awakening has a pretty different attitude than its predecessors.
Gone is the silly romantic pining between vampire and werewolf; jettisoned are the frequent (and frequently boring) flashbacks to period-piece wheel-spinning. In their place is, quite simply, a pretty bad-ass new attitude. Like Fast Five brought a new tone to a tired franchise, and like Punisher: War Zone just went ape-shit-crazy with the over-the-top violence, Underworld Awakening seems to indicate that the filmmakers are well aware of how formulaic the series has become, and for chapter 4 they're just leaning on the carnage button, big-time. The plot sees our mega-hot anti-heroine Selene sauntering around a near-future in which vampire and werewolf plagues have savaged humanity.
Then she meets up with her werewolf hubby (for a second), gets blasted but good, and wakes up in a cryogenic tube 12 years later. Oh, she also has a daughter. If you're already having visions of annoying kids in silly sequels (like that damn kid in The Mummy Returns), you can take solace in the fact that little Eve (India Eisley) is a voracious monster who cannot be controlled. But then a vampire sidekick shows up to help Selene out, an evil scientist kidnaps Eve, and there's a mega-giant werewolf to contend with. (As with all of the films in the Underworld franchise, the monster effects are pretty impressive, while the peripheral CGI work (which is pretty much everywhere) is, well, less impressive. Also the mega-giant werewolf who beats up Selene in Act III is easily the coolest creature the franchise has yet offered.
Clocking in at a smooth 90-some minutes, Underworld Awakening is equally as "disposable" as its three predecessors in many ways -- but it does earn some bonus points for throwing much of the early lore out the window in favor of crazy kinetic mayhem and frequent bouts of goofy gore. One wonders if it was the inclusion of Swedish directors Mans Marland and Bjorn Stein or perhaps franchise boss Len Wiseman simply decided to take Part 4 a little less seriously, but there's often a palpable sense of fun scattered across this otherwise mindless piece of genre fare. It's a sloppy, messy, frankly dumb action/horror hybrid, but at least it moves quickly, delivers the goods, and (finally) brings a small sense of self-deprecating humor to a series that sorely needed it.