Following on from his critically acclaimed debut drama Shell, Scottish writer-director Scott Graham returns with this equally isolated story of difficult familial relations and picking at wounds of the past.

The film follows the eponymous young mother (Ruth Negga) who, following a violent altercation with her abusive boyfriend in the city, flees with her quiet teenage son Bull (impressive newcomer Ben Gallagher) to her remote and religious namesake Scottish island where she lived until she was a teenager.

She tries her best to settle back into a quiet and rural life that she had previously done her best to shake, including getting involved with the local fruit-picking business and attending the stalwart church service.

But it’s far from a simple solution as there are rocky relationships with old friends and family, including childhood best friend Elizabeth (Michelle Duncan) and Elizabeth’s father (Douglas Henshall) who helped raised her before, as he sees it, she abandoned him.

Then there’s the issue of her son’s guilty conscience over what they did that led them to go on the run that’s now slowly eating away at the mother-son relationship and their ability to maintain a veil of subdued normalcy.

Like with Shell, Graham makes effective use of the evocative surrounding landscape to create a keen sense of time and place, at once beautiful and harsh and invoking that feeling of isolation still technically out in the open which mirrors Iona’s state of mind and facility to cope.

There’s also once again a distinct lack of musical score – silence acts as its very own soundtrack here – and gives the film an eerie and disquieting quality.

However, where the deliberate pace and stoic stillness worked a treat with Shell, it sometimes gets in the way of driving things forward here. It’s evident as soon as Iona and Bull arrive on the island that there’s much strife on the horizon as she attempts to reintegrate with a community uneasy at her sudden reappearance. But its commitment to keeping things as low-key and enigmatic as possible – exhibited in the very limited amount of dialogue between the characters – can sometimes lead to things feeling irritatingly lacking rather than complex and ambiguous, prompting confusion and frustration where power and raw emotion should be.

Iona has an alluringly understated aesthetic, mighty fine performances (particularly from Negga) and a keen interest in what guilt, redemption and atonement can mean to a person. But it’s undoubtedly a step down for Graham from a more mature and well-structured first effort to an allusive, less sure-footed directorial follow-up.