How Long Is “Dies d'agost”?

Confused after months of work searching for material to write about a time in history that a journalist had often spoken about, Marc calls his brother David and they set off on a short vacation. But Marc cannot switch off and David takes him further south, to a place where they have heard people come to from far a field in pursuit of a fish with cat-like whiskers. Without realizing, the two brothers travel into unknown countryside where many ups and downs befell their grandfather, and come across a series of drifting characters that submerge them in a lost paradise.