In the 16th Century, after a couple of years away in the confusing wars, Gerard shambles home to take up again with his wife (Baye), who barely remembers him and even suspects that he might be an imposter.
Based on a supposedly true story, this has been quite reasonably transformed into Sommersby, set in the aftermath of the American Civil War, with Richard Gere and Jodie Foster in the Depardieu and Baye roles. One of the things demonstrated by the Hollywoodisation of Martin Guerre is that there is almost no story in the world that can't be redone as a Western.
The original version, an arthouse blockbuster, is well worth a look in conjunction with the remake, which complements it. Take care, though - and note the star-rating - because this title is only available in a dubbed version.