The Debt, a taut thriller that opens in Tel Aviv in 1997, is a spy movie that’s more concerned with the suspense inside a tiny apartment or a messy cubicle than it is with car chases or pyrotechnics. It’s terrifically suspenseful, however, and at times supremely skin-crawly.  It’s also the only movie you’ll see this fall in which you get to watch Helen Mirren—age 66—totally kick ass.

In 1997, we meet Rachel (Mirren) and Stephan (Tom Wilkinson), two long-divorced former Mossad agents. They are national heroes who since their twenties have been credited with the capture and eventual murder of Dieter Vogel, a Nazi doctor whose grotesque experiments performed on concentration camp inmates earned him the nickname “the surgeon of Birkenau.” (Vogel is fictional, but he’s a not-too-thinly-veiled stand-in for Josef Mengele, of Auschwitz).  Rachel and Stephan’s journalist daughter has written a book recounting the events of Vogel’s capture and attempted escape, and how Rachel—after having her face brutally slashed—chased down Vogel and shot him.

But—as we can guess from the expressions Rachel and Stephan wear as they toast their daughter’s success—everything is not as it seems.  When terrible news about their estranged friend and fellow spy David (Ciaran Hinds) reaches Stephan and Rachel, we’re shunted back into 1965, where twenty-five-year-old Rachel (Jessica Chastain) is joining Stephan (Martin Csoskas) and David (Sam Worthington) at a safe house they’ve established in Soviet East Germany.  Rachel’s task is to spy on Vogel—now a gynecologist—by posing as a patient.  (If a Nazi doctor saying “this is my hand, and this is the speculum” doesn’t just make you cross your legs and shudder, you’re a stronger woman than me). Chastain is excellent—doe-eyed but steely—and the dynamic between her and Vogel (Jesper Christensen) is chilling

This portion of the film is a tantalizing look at what the whole movie might have been:  nail-biting, gasp-inducing and by turns romantic, terrifying and exquisitely creepy.  It lingers in all the right places, and gives the three protagonists—especially Chastain—room to do some excellent work.  Shortly after we discover what really happened on New Year’s Eve 1966, the movie shifts back into 1997. Rachel and Stephan are panicking—the truth is dangerously close to coming out, and somebody has to act. Stephan has been paralyzed years earlier in a car-bombing (one of the very few points of reference to modern Israel), and David is out of the picture. That leaves Rachel. “I knew this would happen,” she says to Stephan, as they watch their daughter and grandchildren play on the beach. “I knew we’d have to pay.”

Mirren is a joy to watch when she gets to kick back into spy mode, but the movie gets bogged down in questions about revenge, truth and redemption—few of which get satisfactorily answered—and lots of slogging through dreary Ukrainian villages.  Ultimately, the ending lacks the steady, steely core of the 1965 segments, but it’s a still a satisfying and suspenseful close to what might have been an even better movie.