The premiere episode kicks off with Huw in the depths of a dimly lit warehouse, hot on the trail of an elusive figure. The atmosphere is thick with shadows, and he dials a number on his phone, querying his target's whereabouts while affirming he's cornered 'him.' As Huw ventures through the solitary confines of the warehouse, an unseen assailant strikes from behind, leaving him conscious just long enough to hear a menacing silhouette loom over him, whispering, "Oh Huw, after all this time, you were so close. Catch you later, detective." The scene abruptly cuts to the opening credits as the episode takes a dramatic pause.
Fast forward three years, where Huw and his wife Alice bid farewell to their home for the day. Huw's chatter about his police retirement bash hints at anticipation, while Alice teases him about envisioning a wild night despite turning 55. Their road-crossing neighbor Frank joins the chat, and their camaraderie is palpable.
At the precinct, Huw tidies his desk and bids farewell to colleagues, each encounter tinged with bittersweet nostalgia. One officer apologizes for leaving unfinished business, but Huw dismisses it with a wave. He invites everyone to join him for a farewell drink at the local pub, yet only Jenny, a thoughtful colleague, accepts. She presents him with cufflinks, noting the team's quiet moments, which he acknowledges with a grin. However, his evening falls short of the rowdy celebration he envisioned; the pub greets him with an uneventful silence, much to his disappointment.
Retirement sets in for Huw, but leisure proves a challenging companion. Determined to stay occupied, he decides to repair the freezer at an ungodly hour of 7 AM the next day, much to Alice's chagrin. To fill the gaps in his day, Huw peruses local news on his computer, the temptation to search 'Ripton Stalker'—an unsolved murder case that dogged his career—niggling at him. Instead, he deletes the misspelled query and opts for 'Unsolved Local Cases,' hoping to find something that piques his interest. Ironically, he stumbles upon a podcast dissecting his failures in capturing the Ripton Stalker, and with a frustrated huff, he switches it off.
Huw joins his neighbor, Frank, for a round of golf, their conversation interwoven with murmurs of retirement's unanticipated rigors. Huw's curiosity peaks as he inquires why Frank can't seem to shake off the haunting memory of the Ripton Stalker case. Frank, dismissive, labels regret a futile emotion and urges Huw to embrace his retired life with relish.
Later, while meticulously cleaning his golf clubs, Huw stumbles upon one belonging to Frank, accidentally tucked away in his bag. He promptly heads over to return it, only to find Frank's door unresponsive to his knocks. Worried sick, Huw retrieves a spare key from beneath a garden gnome and quietly lets himself in through the back door. Still, no sign of Frank. Instead, Huw is confronted with a heart-wrenching sight – Frank, lifelessly slumped in the bathtub.
The police arrive swiftly, and to Huw's bewilderment, his former colleague Jenny shows up too. He remarks to Alice about the oddity of Jenny's presence if Frank's demise was a mere heart attack. Jenny, stern, warns Huw to stay out of it, now that he's retired. When she later visits him at home, his probing questions about Frank meet with evasion. Her true concern lies elsewhere – a flash drive containing sensitive data about the Ripton Stalker case, downloaded from the police station computer. Huw's denial falls flat on Jenny's skeptical ears; she knows he's concealing the truth. Despite his repeated inquiries about Frank, she brushes it off as a drug overdose, to which Huw vehemently objects, knowing Frank's drug-free lifestyle. Her sarcastic rejoinder hints at a lack of understanding between them, much like Huw's perception of Frank.
Undeterred, Huw dons gloves and sneaks back into Frank's house. However, his reconnaissance is cut short by Alice's call – she's spotted him from across the street. Deflated, Huw returns home, conceding it wasn't his brightest move.
The following day, Huw listens intently to a podcast revisiting his failed pursuit of the Ripton Stalker case. It delves into the killer's modus operandi: infiltrating victims' homes, observing them while they slept, and tampering with their belongings, toying with their minds for months before striking at their lowest ebb. After each murder, the killer would send Huw a taunting letter, signed off with the chilling phrase, 'catch you later.' The podcast reveals Huw's demotion from the case and the killer's continued elusive status.
Post-funeral, Alice and Huw gaze at Frank's now-vacant house, up for sale across the road. Alice presents Huw with golf balls, urging him to hit the greens and find solace in the game. He complies, yet Frank's absence is keenly felt.
Patrick Harbottle moves into Frank's house, his arrival marked by an encounter with Liz, a flirtatious neighbor. She later joins Alice and Huw for a girls' book club night, announcing her intentions to seduce Patrick, seeking an affair to salvage her struggling marriage.
Huw abruptly exits Alice's book club, only to be met with a peculiar surprise at his doorstep: Patrick, a familiar and affable figure whose amicability strikes Huw as odd. Despite his curiosity, Huw accepts Patrick's invitation to join him, Steve, and Paul, their other neighbors, at the local pub.
Upon arriving, the conversation inevitably steers towards Patrick's occupation as a repairman, while Steve and Paul vent about their jobs, praising Huw for his wise choice of retiring early. They tell Patrick about Huw's remarkable ability to scan a room and absorb details about its occupants that escape everyone else's notice.
To demonstrate his talent, Huw recounts details about the other patrons in the pub—what they're drinking, what they're wearing—all without turning around. The onlookers are mesmerized. As they stroll back home, Patrick and Huw engage in idle chatter, but as they part ways, Patrick's casual farewell, "catch you later," sends a chill down Huw's spine. He recognizes it as the signature phrase of the infamous Ripton Stalker and rushes indoors, where a panic attack ensues.
The following morning, Huw seeks out Jenny, insisting she review Frank's post-mortem report. He's convinced that his death wasn't a suicide. Jenny is irked by his unexpected presence, given his supposed retirement, and it's evident that Patrick's encounter has left Huw unsettled.
Determined to uncover the truth, Huw invites Patrick to join him for a round of golf, hoping to gain more insight into his character. On the golf course, Huw probes Patrick about his past residences and marital history, prompting Patrick to inquire about the reason for Huw's intense interest. Huw reveals that Patrick seems to know a great deal about him already, to which Patrick admits he Googled him. The conversation then turns to the Ripton Stalker case, and though Huw maintains composure, pretending to have moved on, the air between them is thick with tension. It feels like a game of cat and mouse has commenced, culminating in Patrick's poignant question: "What's the most important thing in the world to you, Huw?" to which Huw responds, "Alice."
The next day, Huw awakens to an unexpected sight—it's 9 am, and he's enjoyed his first lie-in in thirty years. He hears voices downstairs and descends to find Patrick enjoying a coffee with Alice. Huw isn't thrilled to see him, but Patrick is there to extend an invitation to a housewarming party, and Alice seems thrilled at the prospect.
At the gathering, Alice and Huw were astonishment to witness the entire street had been extended an invitation. Patrick greeted Huw warmly, expressing his delight at his presence before mingling with the crowd, whereas Huw, curiosity piqued, slipped upstairs for a discreet exploration. In Patrick's sanctuary, Huw rummaged beneath the bed and through drawers, ultimately uncovering a briefcase. However, just as he was about to delve into its contents, Alice intercepted him, insisting they depart immediately.
Upon returning home, Alice confronted Huw, who eventually confessed his suspicion that Patrick was the elusive Ripton Stalker. Horrified, she reprimanded him for succumbing once again to his obsession, reminiscent of past incidents that had left him in shambles. She queried the basis of his accusation, prompting him to reveal his reasoning: Patrick's catchphrase, his familiar vocal tone, Frank's enigmatic demise, and the peculiar circumstances of his moving into the house directly across the street without prior inspection.
Alice's eyes welled up with tears as she recounted how their daughter had grown distant since his last obsessive pursuit of the case. Realizing his actions were causing her distress, Huw vowed to relinquish his fixation.
Meanwhile, at Patrick's abode, he retreated to his chamber to ascertain if the briefcase remained undisturbed. Though he refrained from opening it, he noticed it had been slightly displaced, and Huw's beer bottle resting on his bedside table. A knowing smile played on his lips, as if he had anticipated Huw's clandestine foray.
At the precinct, Jenny scrutinized Frank's postmortem report, as per Huw's suggestion, grumbling to a colleague about her reluctance to indulge him. Yet, upon examination, she was taken aback to discover the cause of death remained inconclusive and necessitated further inquiry.
That evening, as Huw gazed out of his bedroom window towards Patrick's residence before retiring for the night, he was startled to witness Patrick standing motionless on his balcony, his gaze piercing straight through the darkness to meet Huw's.
