Mike, a troubled 15-year-old dropout, secures a job at a public bathhouse in East London. Under the guidance of his co-worker Susan, who is a decade older than him, Mike finds himself entangled in a world that mixes both affection and manipulation. Susan, a playful tease, oscillates between being warm and affectionate to cold and aloof, leaving Mike bewildered by her behavior.
His initiation into the job comes when a female client provocatively pushes Mike's head into her bosom and engages him in suggestive banter about football legend George Best. Initially hesitant and perplexed, Mike is convinced by Susan that these sexual encounters are a customary aspect of their work environment, leading him to contemplate serving some of Susan's female clients for more generous tips.
As Mike grapples with his burgeoning infatuation for Susan, he is painfully aware that she is already engaged to a wealthy young man named Chris. Complicating matters further, Mike discovers that Susan is cheating on Chris with his former physical education teacher, who inappropriately interacts with young girls under the guise of a swim instructor. Consumed by jealousy, Mike begins to trail Susan, attempting to disrupt her dates, which escalates into a chaotic scene at an adult movie theater, where he crosses boundaries that leave Susan furious yet somehow encouraging of his pursuit.
Despite relentless teasing from his peers, Susan's jibes about his mother, and even an incident where she carelessly damages his bicycle, Mike remains steadfast in his infatuation. Rejecting alternate avenues for intimacy—such as with an ex-girlfriend and a prostitute offering discounts—he retrieves a life-sized cutout of a stripper resembling Susan during one of his stalking attempts. This moment ignites a dramatic encounter where he furiously confronts her on the London Underground, demanding answers and leading to a series of bizarre events.
The following morning, Mike creates havoc at a foot race orchestrated by the physical education teacher, culminating in vandalism against his car while Susan is at the wheel. This sets off a chain of events where a furious Susan strikes Mike, unintentionally dislodging a diamond from her engagement ring. In a frantic attempt to recover it, they wind up at the bathhouse to melt the surrounding snow, using electrical wiring to heat a kettle in the empty pool.
In an intense moment, while Susan steps away, Mike unearths the diamond and teasingly challenges Susan, insisting she undress before he hands it over. Ultimately, she succumbs and lies beside him in the pool, leading to a confusing sexual encounter that leaves Mike questioning his own performance.
The tranquility is shattered when Chris calls, prompting Susan to hurriedly dress and prepare to leave. Desperate for her to stay, Mike pursues her around the filling pool, his emotions spiraling out of control. This climax culminates in a dark twist when, in a fit of rage, he strikes her with a ceiling lamp, leading her to fall into the rising water below. As chaos reigns with water engulfing Susan and a live wire ominously hovering nearby, Mike mirrors the intimacy he once shared with the photo cutout, embracing her underwater, their fates intricately tied to the dangerous currents swirling around them.
