The plot of THE DEBT is rather enigmatic and a bit confusing because of the technique of cutting back and forth between past and present. Added to this is an even more problematic factor: the younger and older counterparts don't look a bit alike, so keeping track of them by character names can keep a viewer in a distracted frame of mind.
Other than the script problems, it must be said that the acting is all on a high level, and the story is particularly engaging during the earlier 1967 sequences. This is partly due to the fact that Rachel (Jessica Chastain) gives the most impressive performance in the film and is someone who immediately involves you in the story. She emerges later on into the Helen Mirren image, which is not quite credible in my opinion. Mirren does a fine job as the mature Rachel and her final scenes with the man she has been hunting down is staged realistically with gut-wrenching violence.
If you can get beyond the casting problems involved, the story is taut with suspense but told at a rather leisurely pace.
Tom Wilkinson and Martin Csokas as old and young Stephan; Ciaran Hinds and Sam Worthington as old and young David; and Jesper Christensen as Dr. Vogel give performances that cannot be praised highly enough. The only drawback is that the resemblance between young and old is entirely missing, a fatal flaw when a film is told in cross-cuts between past and present.
Hunting down an ex-Nazi surgeon who has committed war crimes always makes for an interesting story idea...but in this case, there are too many flaws to make the film wholly successful.