At the heart of the very quirky comedy ‘The Incomer’ are siblings Sandy (Grant O’Rourke) and Isla (Gayle Rankin), who live in almost complete isolation on an island off the north-eastern coast of Scotland. Their parents have died, leaving them not simply alone but dependent upon some decidedly unreliable family memories about why they have spent their lives separated from the mainland.

They have effectively been brought up to fear outsiders, and what makes this interesting is that neither really has any experience of the outside world against which to test what they’ve been told. Their understanding of life beyond the island has been constructed almost entirely from their parents’ stories.

Even their family history may not be what they believe. Their mother became ill and travelled to the mainland for treatment before dying, yet they have somehow inherited the belief that had she remained on the island she might have survived. It is nonsensical, of course, but that’s precisely how family mythology can work. Repeat something often enough and eventually it becomes indistinguishable from memory.

Into this strange existence comes Dominic (Domhnall Gleeson), a local government official from the mainland, who informs them that they cannot continue living there and are going to have to leave.

The incomer has arrived. Inevitably Sandy and Isla resist, and their resistance becomes increasingly eccentric, involving strange costumes, rituals and eventually an attempt to capture the threatening outsider. There were moments when the film reminded me of ‘The Wicker Man’, although here the folk-horror imagery is being played much more for quirky comedy.

Yet there is something darker underneath it.

Isla believes in a mythical Selkie living in the sea which communicates with her and attempts to persuade her to enter the water. It reminded me somewhat of Stephen King’s ‘It’, where Pennywise tries to entice a child into the drains. Whatever form the invitation takes, we know that following the mysterious creature into its world is unlikely to end happily.

The Selkie also becomes another representation of the unknown. Isla is simultaneously frightened by the possibility of leaving her familiar environment and attracted towards something beyond it.

In this respect the film called to mind ‘The Truman Show’. Truman has spent his entire life being conditioned to believe that leaving his artificial world is dangerous. Every time curiosity draws him towards the boundary, somebody provides another reason why remaining safely where he is would be preferable.

Sandy and Isla have undergone a similar conditioning in that their island is both home and prison.

They are not being physically prevented from leaving so much as psychologically discouraged from imagining that anything worthwhile could exist elsewhere. That makes ‘The Incomer’ an interesting film about introversion and the comfort zone. If somebody spends their entire life being told that the outside world is frightening, eventually staying still can start to feel like a rational choice.

But, of course, safety and happiness aren’t necessarily the same thing.

There are echoes too of films such as ‘The Ballad of Wallis Island’, where an outsider arrives in a remote community and discovers that the encounter changes both visitor and inhabitants. Dominic initially appears to represent everything Sandy and Isla have been taught to distrust: government, bureaucracy, the mainland and unwanted change.

Yet gradually the distinctions become less straightforward, not least because Dominic is something of an outsider himself. He isn’t the confident representative of civilization arriving to enlighten two isolated eccentrics. He’s introverted and socially awkward, too, and as he spends more time on the island, there is a sense that he may actually be surprisingly comfortable there.

The three characters therefore have more in common than they initially appreciate.

That gives the film its warmth. Dominic brings Sandy and Isla the frightening possibility that there might be a life beyond the island, while they offer him an environment in which his own awkwardness doesn’t necessarily make him unusual.

Underneath its eccentric comedy and folklore, ‘The Incomer’ is therefore about community, inherited stories and the enormous psychological difficulty of stepping outside the world we know.

‘The Incomer’ is ultimately a quirky comedy about three introverted people who initially seem to come from completely different worlds, only to discover that none of them is particularly comfortable in the world they were given.

Sometimes the greatest danger isn’t leaving your comfort zone.

It’s spending your entire life inside it because somebody else told you to be afraid of what lies beyond.