The film sees Partridge in the lead role as Milo, a young man who returns to his late, estranged father’s house in Tuscany for a pivotal weekend. Accompanied by his best friend Zac, played by Jude Carmichael (Dear England), Milo finds himself entangled in a double date with two American travelers. What begins as a promising encounter soon unravels, forcing each character to confront their past selves, their current identities, and what they must leave behind in Italy. The narrative aims to capture the intense, often fleeting, nature of youthful relationships.

One Last Summer is a collaborative effort with Misha Citron, who wrote and directed the film. Citron previously worked with Partridge on Enola Holmes, and their creative partnership has deepened with the co-founding of Pipe Dream Films, the production company behind this new indie feature. Mia Jenkins (Love Me Love Me, Geek Girl) also joins the cast, with further announcements expected.

Partridge expressed his enthusiasm for the expanded responsibilities, telling Deadline, "As an actor and a first-time producer, I loved leaning into true creative collaboration. Our aim being to make the film for ourselves, as young people to enjoy first and foremost." This sentiment underscores the film's target audience and its authentic approach to young adult experiences.

Citron elaborated on the film's emotional core, stating, "I wanted to create a dynamic between the ensemble that reflected the charge and intimacy of youth, feeling the sweetness of attraction that is cruelly muddied by inevitable insecurity, fear, and, often unfortunately at this age, grief." This suggests a nuanced exploration of the complexities inherent in early adulthood.

Beyond Pipe Dream Films, the production also involves Blue Lobster Productions, with Jim Parks (producer of Steven Soderbergh’s The Christophers), Maya Nurmohamed, and Saskia Steinberg serving as producers. The completion of principal photography in Italy marks a significant milestone for the project, hinting at its eventual release.