POSSIBLY the oddest, most unlikely franchise in film history – a series of movies which consists of little more than two people talking.

This third part may appear during the summer blockbuster season, but there are no big bangs, car chases or superheroes flying through the air.

Just an intimate portrait of a couple – American Jesse and Frenchwoman Celine –who met on a train and fell in love wandering the streets of Vienna (Before Sunrise) and met again after he wrote a book about the experience (Before Sunset).

Nine years ago Jesse and Celine are married, the parents of twin girls and living in Paris. They’re nearing the end of an idyllic holiday in Greece.

His teenage son Hank has been visiting. Everything is rosy. At least to begin with – it wouldn’t be much of a movie if something didn’t happen to disturb their happy marriage.

That something is the casual suggestion that they might move to the US to be nearer his son and be a proper dad during his important teenage years. Having lit the fuse, Jesse has to take cover as the explosion – Celine’s less-than-enthusiastic response to this proposed drastic change to their lifestyle – threatens to blow their relationship apart.

Director Richard Linklater stages this domestic disturbance as a series of long conversations between the two of them, apart from a dinner party with fellow holidaymakers, in the car, in the hotel or just walking.

Ethan Hawke and Julie Delpy slip back into their characters with ease, not so much acting as being Jesse and Celine. Do they live happily ever after? Will there be a fourth instalment? That would be telling.