The final episode commences with Pip, still ensconced in Elliot's loft, alongside the enigmatic young woman he had imprisoned there. She reveals that she was sleeping on the streets when Elliot stumbled upon her five years ago. Initially, he mistook her for Andie, but upon realizing she wasn't the one he sought, he offered her a temporary shelter for the night. However, that evening, fueled by alcohol, Elliot confessed a horrific truth - he had murdered Sal. This revelation jolts Pip, as everyone had assumed Sal had taken his own life, a facade skillfully crafted by Elliot.
A flashback takes us to the moment when Elliot confessed to Isla, the woman in the loft, that he had drugged and smothered Sal. Despite feeling remorse, he justified his actions, claiming he had no choice. Isla, horrified, pretended composure, her fear of Elliot palpable. As he left the room, she attempted to flee, but Elliot intercepted her, thus sealing her fate as a captive in his loft.
The police arrive promptly, apprehending Elliot and rescuing Isla, who is whisked away in an ambulance. Pip is finally liberated, and her father rushes towards her, embracing her tightly, a sigh of relief escaping their lips.
The following morning, Pip was ensconced in the warmth of her home, determined to erase all traces of her investigation. She tore down the evidence plastered on her wall, vigorously rubbing off the scribbles, convinced she had solved the puzzle. But had she truly? Pip and Ravi shared a heartfelt conversation, reflecting on the shift in their community's understanding that Sal's death was not self-inflicted and Andie's murder unsolved. Ravi confessed that his parents' emotions were a rollercoaster, but he was finally liberated, free to leave the village and escape the shadow of his brother's fate. Pip's heart sank as she heard of his departure, but a glimpse of Cara at school, their embrace bridging the gap of betrayal, offered a ray of hope for their friendship.
Alone in her room, Pip wept over the collateral damage of her revelation, knowing she had irrevocably altered Cara's life. Her mother's consoling words, affirming her daughter's bravery and pride, only served to intensify Pip's guilt. Then, a nagging thought came to light: if Elliot wasn't Andie's killer, who was? Pip salvaged some discarded evidence and crafted a new timeline, conclusively proving Elliot's innocence in Barney's murder. This revelation sparked a chilling realization: another killer was still at large.
Pip confronted Elliot at the police station, accusing him of Isla's abduction, Sal's murder, and his illicit relationship with a student. Elliot didn't dispute these allegations, but he steadfastly denied killing Barney or Andie. Pip discerned that the menacing texts she had received differed from Elliot's paper threats, suggesting a separate perpetrator. Elliot disclosed that Andie had been desperate for money, fearing her father, Jason. He claimed to have an alibi for the night of Andie's death, attending a dinner party, but he also admitted seeing Jason leave briefly in his blue van while searching for the missing girl. The truth remained elusive, a game of he-said-she-said between Elliot and Jason.
Elliot confessed to Pip that upon Andie's discovery, he knew the evidence would inevitably point to him. Urgency gripped him, so he recalled Naomi's unusual behavior and delved into her diary, uncovering the hit-and-run incident. A sinister idea, a means to safeguard himself, took root in his mind: to eliminate Sal and pin Andie's disappearance on him. He justified it as protecting his daughters, using the hit-and-run as a tool to coerce Naomi and Max into lying to the police, thus validating his narrative of Sal's guilt.
As her session with Elliot concluded, Pip hastened to Ravi, informing him that a killer still remained uncaught. But Ravi, his bags packed and eager to depart, was indifferent to Elliot, the man who had taken his brother's life. Pip pleaded with him to stay, emphasizing their teamwork, but Ravi declared it over, leaving Pip distraught.
Pip ventured to a recycling plant, where a blue van lay concealed beneath tarpaulin. Convinced she had stumbled upon the van Jason used to kill Andie, she was dismayed to find it a mere red herring. Yet, Jessie, the girl who had rescued her from drug dealers at the party, came to her aid once more, sparing her from being caught snooping. Jessie clarified that Jason hadn't left the dinner party to murder Andie; instead, an alarm had rung at the plant, and he was heading out to silence it. Jessie knew this because she worked there.
She recounted that Becca, her best friend, and Andie were wild, leading their father to be stringent with them. Jessie recounted a night when Becca attended a raucous party and awoke elsewhere, raped by an unknown assailant. At home, Pip studied her evidence board and deduced that Max Hastings must have raped Becca. He was the mysterious customer known as TT, who had a penchant for Rohypnol, the drug Andie sold him. Pip confronted Max, and he confessed to sleeping with Becca, but claimed it was consensual. Pip retorted that consent was impossible when Becca was unconscious after being drugged.
After a relentless investigation, we uncovered the culprit behind Andie's murder. Pip pieced together the puzzle, realizing that the last person to see Andie alive was her sister, Becca. Through a series of haunting flashbacks, we witnessed Andie stumbling home, her head dripping with blood—the aftermath of her heated altercation with Elliot.
In the present moment, Pip confronted Becca at her home, where Becca confessed about Max raping her and pleaded with her sister to accompany her to the police station. However, Andie refused to lend a helping hand, as she was the one who supplied Rohpnol to Max, thereby implicating herself in the crime.
Becca revealed to Pip that Andie had intended to flee with Sal the following day, and had resorted to selling drugs to amass funds for her escape. Irritated by Andie's abandonment, Becca lashed out, shoving her sister, who stumbled and hit her head against the door, collapsing in a heap. As Andie struggled to breathe, Becca watched helplessly, her sister's life slowly ebbing away.
Pip emphasized that Andie had already suffered injuries from Elliot, implying that Becca wasn't solely responsible for her death. Unfazed, Becca shrugged off the accusation, asking if Pip wished to see where she had concealed the body. Pip nodded, but Becca insisted she finish her tea before they departed.
As they ventured deeper into the cavernous darkness of the caves, where the fateful calamity party had unfolded, Ravi experienced a change of heart. He disembarked the bus and hastened home, only to find Pip's car parked outside Jason's abode. Fearing that Jason had harmed Pip, given her suspicions about his involvement in Andie's death, Ravi sought Cara's assistance, despite the strained relationship stemming from her father's involvement in his brother's demise. Leveraging her technological prowess, Cara tracked Pip's phone, revealing her location in the woods. The pair hastened to her rescue, determined to save Pip from whatever perils awaited her.
Deep within the cavernous darkness, Becca led Pip to a hidden well, revealing the grim truth of where she had discarded her sister's lifeless body. With a sinister glint in her eye, she informed Pip that she would now have to join her sister in that abyss, for she knew the truth. Pip, realizing she had been drugged with Rohypnol, fought back with all her might, managing to flee but ultimately succumbing to the drug's effects, collapsing in the cave's shadows.
Just as Becca dragged Pip's limp body towards the well, Ravi and Cara appeared, their timely arrival saving Pip from an unthinkable fate. The police were summoned, and Becca was apprehended before she could escape.
In a fleeting memory, we see young Pip in the school corridor, Sal inquiring about Andie's whereabouts. It was revealed that Pip wasn't hiding from Andie; she was fleeing from her own father. Pip confided in Sal that her father knew everything, and they decided to flee together the following day, professing their love for each other, unaware that their lives were hanging by a thread.
After uncovering that Becca was the one who had struck the fatal blow to Andie, Pip realized she was the one sending the ominous texts, watching her from the shadows of her garden, and even the culprit behind the murder of her beloved dog, Barney.
Returning home, Pip revealed that she had completed her EPQ, choosing to delve into Andie's case. Her mother praised her work, but Pip confessed her doubts about attending Cambridge, wondering if she was merely following in her father's footsteps. Her mother encouraged her to follow her heart, promising to support her in whatever path she chose.
With renewed resolve, Pip confronted Max, her words sharp and unforgiving. She revealed that he was the source of all the evil in this case, vowing to fight until justice was served for every victim he had wronged. Max was left speechless as Pip walked away, her triumph palpable in the air.
