As the story opens, we meet Evey (Natalie Portman), who is out after curfew and falls foul of the brutal secret police. She is rescued from them by the masked anarchist "V" (Hugo Weaving) who unintentionally gets her in worse trouble as she is captured on surveillance camera in his company as he blows up the Old Bailey in the name of Justice. What happens after that is a powerful, dramatic, and sometimes brutal story that unfolds the origin of "V" as it is entwined with the rise and eventual fall of the corrupt government of "arch-Chancellor" Adam Sutler (John Hurt).
The film raises good issues of conscience, freedom, and the costs of security. "V" is pretty clearly a "freedom fighter" rather than a "terrorist" at least to the audience, but one could legitimatly ask how justified, and how effective, some of his tactics might be. (In true movie hero fashion, he manages to accomplish even major actions without apparent harm to innocents--.)
Portman and Weaving are well supported by a distinguished cast of British actors, including the aforementioned Hurt, who spends most of the movie expostulating on a big screen from an "undisclosed location", Tim Pigott-Smith as the creepy chief of secret police, and Stephen Rea, the honest cop tasked with tracking "V" down. All Weaving's acting has to be carried by voice and action, and he does very well. Portman is excellent, also.
This film has my highest recommendation. All who can should see it. The movie is rated R for strong violence and some language.