via Geeks of Doom
Kate Beckinsale returns to the role of Selene, the fearless werewolf-killing vampire assassin and heroine of the first two Underworld films. She sat out of the 2009 prequel Rise of the Lycans. From what I’ve seen in the trailer, Beckinsale appears to be the only cast member from any of the first three films returning for Awakening, but that could be subject to change.
The plot focuses on Selene as she emerges from a cryogenic nap to face a new world where the battle between the vampires and their mortal enemies, the Lycans, has now been joined by the humans, who hunt them both. Much blue-tinted, slow-motion action with Beckinsale jumping about and firing twin pistols while wearing the tightest of skintight leather outfits ensues, just like in every movie in the Underworld series.
More Details (including Comic Con Panel coverage) here