Morvern Callar, a young woman residing in a quaint port town in Scotland, juggles her job at a supermarket and her unexpected journey through grief. On Christmas morning, her world is shattered when she discovers that her boyfriend has taken his own life, leaving behind a poignant suicide note, a mixtape, gifts, funeral money, and the manuscript of his unpublished novel—dedicated to her. In a moment of profound emotional turmoil, she chooses to erase his name from the manuscript and replace it with her own before sending it off to the publisher mentioned in his final letter. Alarmingly, Morvern decides against notifying the authorities and leaves his body undisturbed.
When her best friend and coworker, Lanna, inquires about the situation, Morvern fabricates a story, claiming her boyfriend has left her to start anew abroad. After a few days of struggling with the reality of her situation, Morvern takes drastic action; she dismembers the body and buries it in the treacherous mountains, scrubbing the flat clean of any evidence of her crime before inviting Lanna to stay with her.
Amidst the unfolding chaos, she receives an encouraging letter from the publisher expressing interest in the manuscript and responds by indicating that she will be away on holiday in sunny Spain. The shadows of betrayal soon cast doubt on her friendship when Lanna confesses to having had an affair with Morvern's late boyfriend, igniting a wave of anger within Morvern. Despite the tension, she chooses to bring Lanna to Spain, hoping to escape their troubles and embrace the vibrant nightlife together.
While at the hotel, Morvern encounters a man mourning the recent loss of his mother, leading to a fleeting romantic encounter. However, her fickle nature shines through as she abruptly demands they leave the hotel the following day. Their journey takes an unfortunate turn when they get lost on a rural road, culminating in a tense standoff between the two friends as Lanna grows weary of Morvern's increasingly erratic behavior. By morning, they part ways, with Morvern rejoining her path toward the publishers who have come to Spain, eager to secure rights to the manuscript.
In a twist of fate, Morvern feigns authorship of the novel and accepts an astounding £100,000 advance, a decision that sends her spiraling deeper into deception. Upon returning to Scotland with her newfound wealth, she invites Lanna to join her in Spain once more, only to be met with rejection as Lanna chooses to remain anchored in her life back home. With her suitcase in tow, Morvern heads to the railway station, where she immerses herself in the nostalgic sounds of "Dedicated to the One I Love," a haunting track from the mixtape left to her by her boyfriend, echoing her complex web of grief and newfound identity.
