In September 1969, Camden Town finds itself as the backdrop for the misadventures of two out-of-work actors, Marwood and Withnail. Residing in a dilapidated flat with their solitary visitor being the drug dealer Danny, Marwood's discontent with their stagnant lifestyle grows unbearable. In a bid for respite, he convinces Withnail to seek refuge at his Uncle Monty's rather peculiar country cottage.
Uncle Monty, an eccentric man with a penchant for theatrics and an undeniable attraction to Withnail, invites them over to his Chelsea home. During their visit, Withnail indulges in white lies about his acting success while Marwood desperately tries to escape their chaotic lives. After their visit, Withnail manages to secure the keys to the cottage which sets the stage for their rural escapade.
Their arrival at the cottage brings a stark realization—this countryside experience is far from what they envisioned. The duo resorts to desperate measures, including burning Monty's furniture for warmth and grappling with the ethical dilemma of butchering a chicken. A trip to the local pub introduces them to a rowdy bartender and a brash poacher named Jake, who belittles their antics. Amidst a backdrop of drunken escapades, Withnail's ill-fated fishing trip erupts in chaos when, in a moment of panic, he accidentally discharges his shotgun, leading to mounting tension between him and Marwood.
As the strange holiday unfolds, the presence of Uncle Monty looms heavily. Marwood, feeling increasingly uneasy around Monty’s advances, devises an escape plan while Withnail, oblivious to the undercurrents, revels in Monty's company. Their brave stand against the absurdity of the situation leads to a night filled with cards and drunken revelries, only to be interrupted by Monty locking Withnail in a room, causing further distress for Marwood.
Marwood’s anxiety peaks as Monty, dressed in his robe, intrudes upon his solitude, awakening feelings of confusion and dread. Monty reveals that he has been led to believe in Withnail's fabricated life, having been told about their supposed relationship. In a moment of panic, Marwood spins a tale, claiming he and Withnail are actually lovers, which leaves Monty heartbroken and ashamed.
Confronting Withnail about the web of deception, Marwood learns that the cottage was an unexpected ability to escape their grim realities. A telegram arrives for Marwood, offering a glimmer of hope—a lead role not just any job, stirring a mixture of excitement and dread.
The return to their squalid flat presents a daunting new chapter as they discover the chaos left in the wake of their absence. The news of Marwood's breakthrough sends them on separate paths; while Marwood preps for a new beginning, Withnail grieves the impending loss of their friendship. Their last moments shared during a rainy farewell become a poignant memory, with Marwood asserting he needs to move on, even if it means saying goodbye.
As Marwood walks away to embrace his future, Withnail, lost in his solitude, performs a heartfelt rendition of Hamlet’s soliloquy for any wandering audience, leaving him standing soaked in emotion, a lost man in a world moving on without him.
