Rhona Mitra plays the lead female character, Sonja. In the first Underworld film, Sonja is introduced into the story via a memory that had happened centuries earlier and was killed by her father Viktor - who is a Vampire Elder. I loved how this film is digging a bit more into the past as I do remember wondering about the Sonja character and the storyline involving her.
Michael Sheen plays Lucien and Bill Nighy as Viktor - both are lead male characters. Although Rhona did a great job, Michael and Bill stood out by miles. Their performances were amazing, facial expressions were surreal... expressions I'm sure I'd never seen before but were just always so perfect for the scene. I was so impressed that I really feel I can't ever watch these two actors in other films for fear it will ruin my outlook! Michael Sheen had played ex-British Prime Minister Tony Blair and after seeing the trailer, I definitely can't watch it. However, on another note, he is playing the Cheshire Cat in the 2010 Alice in Wonderland film (yes they're making a film!), and that I can't miss!
The 'romantic' part of the film, (which I feel is always important if there is a lot of action) is the love between Sonja and Lucien, Vampire and Lycan. It is of course kept as a secret because Viktor sees that Vampires are the more superior race and Lycans as slaves. Viktor kills Sonja with Lucien watching and unable to save her because she revealed that she is pregnant with Lucien's child, and Viktor will not allow the bloodline to be spoilt. This was all very dramatic and I loved it!
I also quickly realised while watching the film that viewers will really empathise with the Lycans, which was weird at first because Lycans were perceived as the 'bad-guys' in the first film. I am so glad they made a film based on this unique race as I found the story fascinating and feel there is still a lot more to be told. However, I have read that the fourth Underworld will continue from Underworld Evolution (#2), which is set in modern time and will be about Selene... but this is all speculation.
There is so much more storyline in between what I have already mentioned, it is very deep but they all interconnect with each other and it is wonderful to see it develop amongst the series. You really start to appreciate the meticulous, detailed thought that has gone into each film. One thing that really stood out however, is that in the first one where Sonja's death is remembered, the actress playing her is blond, but Sonja in #3 is dark haired. Just a bit irritating, but something I can forgive! The costumes were also fantastic as it is set in a medieval time period... so instead of the black, glossy spandex catsuit and corset that Kate Beckinsale wore as Selene in the first two Underworlds, Rhona Mitra utilises the leather and chainmail look. Viktor also wore the most amazing embellished cloaks, which I wish was shown in more detail!
Overall, I loved it and I love the Englishness of it. I also sometimes see it as an older version of Twilight but it's primarily because of the confliction between Vampires and Werewolves. I also wondered that with the second Twilight film 'New Moon' in production, I am curious how they will 'make' the wolves look, because it has to look different to the Lycans from Underworld. I completely recommend this film if you like vampires, action, heroines and a deep storyline - and it doesn't even matter if you haven't watched the other two yet.