In a quaint, isolated fishing village in Ireland, Aileen (Emily Watson), a shift manager at the local seafood processing plant, struggles to navigate her life while working alongside Mary (Marion O'Dwyer), a mother grieving the recent drowning of her son, Mark, and Sarah (Aisling Franciosi), a woman caught in the throes of marital issues with her husband Francie (Brendan McCormack). The atmosphere is somber, especially as the community mourns. However, things take an unexpected turn when Aileen’s estranged son Brian (Paul Mescal) returns home after an unexplained stint in Australia. This reunion, while initially uplifting, takes on a complicated undertone due to the dynamics of the relationships involved.
At the funeral reception for Mark, Aileen feels a surge of hope as she reunites with Brian, alongside her husband Con (Declan Conlon), daughter Erin (Toni O'Rourke), who recently had a baby, and Aileen's father-in-law Paddy (Roddy), who is sadly unresponsive due to a vegetative condition. While Brian remains reticent about his experiences in Australia, he expresses a desire to revive the family’s oyster trapping farm, which had been neglected during his absence. Yet, lacking resources, Aileen makes a dubious decision: she steals oysters from her workplace to support his venture, an act seen by Sarah, creating ripples of tension and unease within the community.
The next day brings alarm as Francie, the local seafood supplier, discovers missing oysters from his order, causing an uproar that Aileen tries to deflect onto a junior worker. Meanwhile, Sarah grapples with the emotional turmoil of her failing marriage as she copes with the fallout of her choices. Con confronts Brian, accusing him of fishing from others' traps, leading to a confrontation that drives Brian to seek work elsewhere. Meanwhile, Aileen is left to navigate her unraveling family dynamics in a spiraling series of events.
As the days unfold, a local disaster strikes; a fungus contaminates the oysters, resulting in a moratorium that devastates the village's economy. This incident coincides with Sarah fainting, revealing the mounting pressure gripping her life. Aileen receives alarming news from the police regarding a sexual assault claim against Brian, who insists he was home with her that night. Aileen, faced with a dilemma, lies to protect her son, which sets in motion a chain reaction of guilt and suspicion.
As secrets begin to unravel in the tight-knit community, Sarah confides in Erin about the truth of what happened, igniting a devastating series of events that lead to a court case. Despite Aileen's attempts to shield Brian by lying about his alibi, the court dismisses the case for lack of evidence, throwing Sarah into despair and leading to her dismissal from work due to her frequent absences. The tides of the community turn against her, and Aileen finds herself ensnared in the repercussions of her actions; she becomes the target of gossip and disdain as Sarah's past comes back to haunt them both.
In the aftermath of Paddy's unexpected death, tensions reach a boiling point. At the wake, Sarah confronts Brian, leading to an explosive reaction that culminates in a physical fight between him and Con. The emotional turmoil escalates, prompting Aileen to confront Brian about his past actions against Sarah, a conversation that concludes with his dismissal of her concerns. As the rising tide threatens the safety around their oyster plots, a tragic and harrowing climax ensues when Brian, scorned and overwhelmed, drowns, leaving Aileen shattered.
In the poignant closing moments, Aileen implores Sarah to remain in the village, but Sarah, feeling the weight of her past and the town's judgment, chooses to leave, confidently setting off to embrace a fresh start away from the shadows of her former life. Aileen is left to reckon with the chaos of her decisions while reflecting on the bonds of family, sacrifice, and the haunting consequences of choices made in desperation.
