Wallace, portrayed by Daniel Radcliffe, finds himself in a stagnant life, dissatisfied with his dead-end job and living with his sister, Ellie, played by Jemima Rooper, and her son, Felix, whose character is brought to life by Lucius Hoyos. After a painful breakup that saw him drop out of medical school—prompted by the realization that his girlfriend was cheating on him with his anatomy teacher—Wallace has become a recluse, avoiding social interactions for the last couple of years.
His friend Allan, acted by Adam Driver, finally drags him to a party where boredom quickly sets in. In an attempt to amuse himself, Wallace starts arranging fridge magnets into whimsical phrases. During this amusing distraction, he encounters Chantry, portrayed by Zoe Kazan, and they strike up a conversation. Meanwhile, Allan begins flirting with Nicole, played by Mackenzie Davis.
After the party, Wallace walks Chantry home, only to discover that she is already in a relationship. Despite this, she gives him her phone number, but he hesitates to pursue anything further. His indecision fades after they unexpectedly meet again at a movie theater, leading to dinner together. As their friendship deepens, Wallace is introduced to Chantry’s long-term boyfriend, Ben, played by Rafe Spall, who works for the United Nations.
Their first encounter at Ben and Chantry’s home takes a chaotic turn when Wallace accidentally runs into his ex-girlfriend, which coincides with Ben’s hospitalization following a series of mishaps. As life unfolds, Ben is required to relocate to Dublin, leaving Chantry and Wallace to explore their growing connection on their own. During this period, Chantry’s sister, Dalia, attempts to come onto Wallace, but he refrains, fearing it could jeopardize his chance with Chantry. Unfortunately, Dalia only exacerbates tension between the two by speaking ill of Wallace to Chantry.
In a twist of fate, Allan marries Nicole, and they invite Wallace and Chantry to a night walk on the beach that culminates in mischief. They find themselves skinny dipping, only to have Allan and Nicole steal their clothes, forcing them to share a sleeping bag on the beach. Feeling awkward about the situation, they leave the beach in frustration the next day.
Chantry receives a job offer that requires her to travel to Taiwan, but the pressure of her faltering relationship with Ben leads her to visit him in Dublin. There, she realizes that his job demands will keep him away often, prompting the two to break up. Wallace, unable to suppress his feelings, decides to follow her there. However, upon his arrival, he faces Ben’s wrath and a surprise punch that sends him tumbling down the stairs. After checking his voicemail, Wallace learns that Chantry has returned to Toronto.
Their reunion is bittersweet, with Chantry reacting poorly upon discovering the extent of Wallace's feelings and the reason for his journey. In contemplating a return to medical school and seeking closure in his life, Wallace attends Chantry's farewell party where emotions come to a head during a heartbreaking goodbye. They finally confess their mutual feelings while sharing a Fool's Gold Sandwich, a lighthearted topic they previously bonded over.
The film concludes 18 months later, as Wallace and Chantry begin a new chapter together in Taiwan, where they plan to nurture both their relationship and Wallace’s medical training. The story wraps up with their return to Toronto, culminating in a joyful marriage.