The trailer begins with Lindy (Beckinsale) waking up in a white room undergoing treatment. Lindy tells the viewer she has a condition where she snaps into violent rage, as a flashback shows her stabbing a rider on the subway.
The treatment installed an electric device in Lindy's body. Lindy can shock herself out of her rages, but can only use it so much before she can't take the shock anymore.
When Lindy doesn't control her rage, she's able to fend off attackers. After Lindy's lover is murdered, she takes matters into her own hands and fights off numerous armed men. Lindy displays the sort of martial arts prowess Beckinsale also displayed in the Underworld movies.