As the old cliché has it, the road to hell is paved with good intentions, and the film The Debt is a cerebral thriller that explores how the actions of a handful of idealists take a turn for the worse and lead them down a path of lies and deception they're forced to follow decades later. On one hand, The Debt is a story full of action and suspense, tracing a game of cat and mouse that takes many years to play itself out, while at the same time it deals with ethics, honor, moral responsibility, and the greatest crime of the 20th century. If the movie doesn't always do an ideal job of juggling these two sides of its nature, it does so well enough to be compelling entertainment that's exciting, clever, and thoughtful. The Debt opens in 1997, as Rachel Singer (Helen Mirren) and her former husband, Stephan Gold (Tom Wilkinson), are appearing at a luncheon celebrating the publication of a book written by their daughter, Sarah (Romi Aboulafia). Rachel and Stephan seem proud but a little awkward, which could easily be chalked up to modesty; the former couple were agents for the Israeli intelligent agency Mossad in the 1960s, and the book recounts how they tracked down, captured, and executed notorious Nazi war criminal Dieter Vogel (Jesper Christensen), known as "the Surgeon of Birkenau" for the hideous medical experiments he performed on inmates at the Third Reich's death camps. However, as we view the events in flashback, it seems the story as it has been told over the years -- often by Rachel and Stephen themselves -- doesn't entirely cohere to the facts. In 1965, Rachel (played as a younger woman by Jessica Chastain) and Stephan (played as a younger man by Marton Csokas) slip into East Berlin from Tel Aviv, where with their colleague David (Sam Worthington) they are to take part in an undercover mission to capture Vogel, who is working under an assumed identity as a gynecologist, and bring him to Israel to stand trial. The three agents are living and working in close quarters, and while their dedication to their mission is great, as Rachel and David pretend to be man and wife as part of their cover, they become infatuated with one another. However, one angry evening Rachel sleeps with Stephan, who is clearly attracted to her, and she finds herself pregnant with his child. The kidnapping is a success, but bringing Vogel back to their safe house doesn't go as planned, and the headstrong Stephan fabricates a lie that will save them from reprisals by Mossad and make them sound heroic to their peers. Despite their reservations, Rachel and David agree to stick to the story, only adding to the tension of the romantic triangle. Thirty years later, Rachel and Stephan's status as Israeli heroes is threatened when they learn that a journalist may have evidence that exposes their lie; with David dead and Stephan now confined to a wheelchair, Rachel sets out to silence a man who could ruin them and rewrite a chapter of her nation's history. Helen Mirren fittingly gets top billing in The Debt even though Jessica Chastain ultimately racks up more screen time as Rachel. While Chastain may have more scenes here, she seems to follow Mirren's lead on how the character should work onscreen rather than vice versa, and Mirren gives Rachel a strength and determination that Chastain mimics well, at the same time adding a level of remorse and responsibility that serves the older character well. There aren't many women in their sixties who could convincingly play an intelligence agent chasing down a target with deadly intent, but Mirren pulls it off with flying colors, merging anxiety and ruthlessness with a deft hand. And if Chastain's attempts to give Rachel a bit of youthful vulnerability sometime seem at odds with the rest of the character, she gets her beauty and sense of purpose just right. Tom Wilkinson doesn't fare quite as well as Stephan, though he's admittedly given far less room to work in his role; Marton Csokas' showy arrogance defines the character, and the older and weaker man doesn't stand a chance. Sam Worthington has the thankless task of playing the tortured nice guy in this story, and he has a hard time bringing color or texture to a role that seems a bit short on either, though he at least makes the character seem noble. And Jesper Christensen gets the nuances right as the Nazi surgeon, revealing his talent for emotionally manipulating those around him and giving even his most compassionate moments an air of foreboding ugliness. Director John Madden takes The Debt seriously as a thriller, and the action scenes are strong and efficient while he generates an admirable tension during the scenes of the young agents training and looking after their quarry. At the same time, he's clearly just as interested in the ethical and political quandaries that lie at the heart of the story, and it sometimes feels as if Madden is trying to give them both equal weight, even when the action elements are obviously tipping the scale. In a season in which we've had more than our share of empty-headed action pictures, it's admirable that Madden has tried to make a thriller that appeals to the intellect as well as offering a dose of suspense and a shot of adrenaline; however, the formula sometimes works against the film's rhythms, and the austere tone of the middle section feels a bit at odds with the more colorful and aggressive tone of the last act. Not every piece fits perfectly in The Debt, but nearly all the individual elements are strong, and enough of them mesh to make this an effective and thought-provoking entertainment.