A stellar cast, perfect pacing and a fresh take on the British spy genre make this Sundance Channel mini great.

Having already scored with its two previous scripted ventures -- Carlos and Appropriate Adult -- the Sundance Channel keeps its streak going with Restless, a superb two-part miniseries about British spies in the 1940s as the buildup to World War II is under way. With an excellent cast and a stirring story (it frays a bit near the end, though not enough to do any damage), Restless is based on the book by British novelist William Boyd (who also writes the teleplay) and has enough intrigue, deceit, twists and lingering suspicions to lure you into its web.

The miniseries stars Hayley Atwell (Captain America), Michelle Dockery (Downton Abbey), Rufus Sewell (Pillars of the Earth) and the dynamic acting duo of Charlotte Rampling and Michael Gambon. It's executive produced by Hilary Bevan Jones (State of Play). That's a lot of talent.

Restless begins in 1976, with Ruth Gilmartin (Dockery) racing down a country road with her son to see her mother, Sally (Rampling). Ruth has been a free spirit without much contact with her mother and kept the secret of having a baby from Sally for years. Turns out everybody in Restless has a pretty big secret, but none more than Sally, who soon drops a bomb. Her real name is Eva Delectorskaya, and she was one of the top spies in the British Secret Service and instrumental in the war effort. (There's not a whole lot of laughs in the tense Restless, but Dockery gets one while also being completely believable as she looks incredulously at Sally and says, "So I'm half-Russian?")

The film then flashes back to Sally's early years where, as Eva, she's played by Atwell, who is really the primary star of Restless, along with Sewell, who plays Lucas Romer, the spy who recruits her.

The premiere is the stronger of the two episodes, but all of Restless is excellent. The first part sparkles as Eva, at first wide-eyed, blossoms with her training. She's a natural. Atwell gives her an earnestness that's fresh for a spy story, but she's also able to convince the audience that Eva's cunning and determination are what separate her from the pack -- not some bad-ass attitude.

Restless deftly switches between the early 1940s and present-day 1976, and much of that has to do with Rampling's superb work. Dockery also is impressive, and the rest of the performances, even the smaller ones like Gambon's, are enthralling.

Airdates Friday, Dec. 7 at 9 p.m. and Friday, Dec. 14 at 9 p.m. (Sundance Channel)