In the fifth episode of Sweetpea, the tension ratchets up as Rhiannon's web of lies and deceit begins to unravel. The episode, titled "Someone's Been a Naughty Girl," sees Rhiannon's kill list expanding to include those who are searching for Julia, as well as herself for her missteps in her reporting aspirations.
The episode opens with Rhiannon's growing paranoia as the town rallies to find Julia, and she becomes a target of suspicion. At the police station, Detective Farrow voices her suspicions about Rhiannon to her superior, but the DI remains unconvinced, focusing on Julia's fiancé, Marcus, as the primary suspect.
Rhiannon's world is further complicated when AJ, her coworker and potential love interest, visits her home under the guise of checking up on her. His visit is cut short by the sounds of Julia, leading to a misunderstanding that Rhiannon is with Craig, her former fling. AJ's departure is followed by a violent outburst from Julia, who attacks Rhiannon with a broken plate. The confrontation leads to Julia being injured, forcing Rhiannon to hide her in the bath to stem the bleeding.
In a moment of vulnerability, Rhiannon and Julia bond over their shared misery. Julia's scars from Marcus's abuse are revealed, and she finally apologizes to Rhiannon for her past bullying. However, Julia's belief that Rhiannon is still a victim plays into Rhiannon's growing frustration with her own life.
Farrow's investigation takes a turn when she discovers Julia's car at the construction shop owned by Rhiannon. The missing CCTV footage only adds to her suspicions, but she is unable to find concrete evidence to link Rhiannon to the crimes.
Craig's questioning by the police provides a tense moment, as he requests to speak with Rhiannon. Dressed and ready for a date, Rhiannon faces a dilemma when Julia offers to do her makeup, leading to a near-fatal encounter with an eye pencil. Julia's hesitation to kill Rhiannon suggests a shift in their relationship, as they consider whether their fates could have been different if they had been friends.
Rhiannon's date with Craig is a farce, as she endures his poor cooking skills to keep him from revealing her presence at the time of his meeting with Julia. Back at work, Rhiannon and AJ are assigned to cover the search party, where Rhiannon is confronted by Farrow, Marcus, and Jeff, each with their own suspicions and dirt on her.
Farrow's theories become more outlandish as she suspects Rhiannon of killing her own father to cover her tracks. The DI dismisses her theories, focusing on Julia's disappearance. The search party becomes a battleground for Rhiannon, as she navigates the suspicions of Farrow, the hostility of Marcus, and the probing questions of Jeff.
A confrontation between Rhiannon and Marcus turns deadly when Jeff witnesses Rhiannon about to stab him. Jeff's subsequent death by oncoming traffic leaves Rhiannon shaken, but she is saved from suspicion when Marcus, via text, threatens her. This leads Rhiannon to hatch a plan to frame Marcus for the murders, offering a way out for both her and Julia.
Farrow's investigation leads her to question Craig, who hesitantly covers for Rhiannon. Farrow's suspicions are raised, and she attempts to search Rhiannon's house, only to be stopped by Sergeant Rory.
Rhiannon and Julia's plan to frame Marcus comes to fruition at Julia's new apartment. They set a trap for Marcus, intending to have him touch the knife that will be used to free Julia. When Marcus arrives and frees Julia, his jealousy turns to rage, leading to a violent confrontation. Rhiannon's push sends Marcus over the edge, and he falls to his death.
The episode ends with the police arriving at the scene, and Farrow looking up to see Rhiannon and Julia standing over Marcus's body. The implications of this final scene set the stage for a thrilling conclusion to the season, as Rhiannon's actions have now led to a murder with witnesses, and her carefully constructed facade threatens to crumble around her.