As dense as a Watergate-era newspaper and as immediate as a blog, State of Play is an absolutely riveting state-of-the-art “big conspiracy” thriller. It’s an often brilliant collision of political scandal, murder, a privatizing military and the rapidly evolving journalism that may (or may not) remain democracy’s watchdog once newspapers, “instant history,” are rendered history by a culture that has abandoned them.

An all-star cast headed by Russell Crowe and Ben Affleck Americanizes (somewhat) and gives the Hollywood touch to what began life as a terrific BBC-TV thriller in 2003. It’s the story of a scruffy but accomplished reporter (Crowe) using and protecting his college roommate (Affleck), now a congressman, when the House member’s secret girlfriend mysteriously dies and scandal erupts.

Reporter Cal suspects there’s more to this death than a simple DC subway suicide. His rattled onetime pal, Congressman Collins, seems to catch on, too. Maybe a Blackwater-ish defense contractor that is being investigated by Collins is to blame.

Cal reluctantly brings in the Washington Globe’s fresh-faced and snarky new political blogger (Rachel McAdams) on the story. “I’m just trying to help you get a few facts in the mix the next time you upchuck online.”

The veteran reporter forgets his ethics as he digs for his friend and sees connections between the subway suicide and a murdered pickpocket. The blogger struggles to learn the basic legwork of reporting on a story that has murderous implications.

Robin Wright Penn is the wife wronged by the affair, Jeff Daniels is the political heavyweight struggling to do damage control and Helen Mirren as the feisty editor curses and demands a story “before it’s ready.”

State of Play is an embarrassment of acting riches, with Oscar nominee Viola Davis having a one-scene cameo as a coroner, Jason Bateman making a brief, pivotal appearance and Harry Lennox as that most hard-boiled of hard-boiled cops.

“Who do you think I am, Bambi’s baby brother?”

In condensing the British series (set in London at Parliament) into a compact two hours, some of the political flavor is lost and some of the surprises, frankly, spoiled — revealed abruptly. But the charismatic cast, brisk pacing and snappy dialogue (writers Billy Ray, Matthew Carnahan and Tony Gilroy are credited) mask some of those shortcomings. Crowe makes his character the life of the piece, quick-witted, sarcastic, bluff and smart. But is Cal as smart as he thinks?

State of Play is a puzzle picture, all too ready to take us down one primrose path only to trip us and make us consider another. And then another. The last of those misdirections seems unnecessary, but director Kevin Macdonald (The Last King of Scotland) keeps the pulse pounding and the mind racing as he juggles the film’s several plots, always with his ear tuned to the last word of that title: Play.

****State of Play

Starring: Russell Crowe, Ben Affleck, Rachel McAdams, Robin Wright Penn, Helen Mirren, Jeff Daniels

Rated: PG-13 for some violence, language including sexual references, and brief drug content