Here is an intriguing cine-novella from Georgian film-maker Tamar Shavgulidze, which is at first unassumingly contemporary and realist, but which then takes a deadpan left turn into something really strange; it becomes like something from the 1960s counterculture, yet is as coolly paced and controlled as everything that has gone before.

Initially, Comets seems like a straightforwardly bittersweet “reunion” tale, full of poignant regret. Nana (Ketevan Gegeshidze) is a middle-aged widow who is pottering about her garden one sunlit afternoon, squabbling mildly with her grownup daughter Irina (Ekaterine Kalatozishvili), when suddenly they have a visitor: a rather stylishly attired woman of Nana’s age, also called Irina (Nino Kasradze). This is the person with whom Nana had a semi-secret love affair when they were teenagers, which caused much local scandal. Irina ran away to begin a glamorous existence in Krakow and Berlin and Nana blandly (or perhaps penitentially) stayed in her home town and had children: Irina is of course named after her lost love and like the older Irina she exasperates Nana by wearing sunglasses to conceal her mood.

There is much sadness in Nana’s life, particularly in her relationship with her late husband. The two women’s conversation now is interspersed with flashback scenes of them together in this very same garden, the two being played as teenagers by Mariam Iremashvili and Nina Mazodier. What is there between them now? Reproach? Sadness? Or a flash of something else — maybe that they could still revive their old feelings, because what on earth have they got to lose? Love is a comet that blazes into our lives all too rarely.

But could it be that as young people Nana and Irina experienced something else: something even more unearthly and exalting and intergalactic? A visitation of something rich and strange, something that made sense of how alien they felt? An interesting experiment in the alternative reality that is love.

• Comets is available on 18 January on Mubi