Episode 4 of Joan commences with a palpable sense of unease, as Joan and Boisie return from their sojourn to procure an engagement ring, only to be met by the ominous presence of the police at their antique shop's doorstep. Their inquiry revolves around a recent heist of an ancient masterpiece, further fueling Joan's fears of losing Kelly forever. Desperate, she implores Boisie to abandon their illicit ways and dispose of the stolen painting, yet her partner's love for art proves stronger, prompting a stalemate.
Later, a social services officer gently deposits Kelly at Boisie's abode, where Joan shares the joyous news of their impending nuptials. The sight of Kelly serves as a catalyst, convincing Boisie of the need for a clean slate—albeit with the contingency of first liquidating the painting. He orchestrates a clandestine meeting with Albie, who cunningly suggests a high-stakes sale to the IRA. Faced with limited avenues, Boisie reluctantly consents.
Joan, determined to turn over a new leaf, proposes a transformation of their antique shop into a sparkling jeweler's haven and embarks on a dedicated course to hone her craft. Amidst the whirlwind of preparations, Joan and Boisie exchange vows in a heartfelt ceremony, though the festivities are briefly interrupted when Kelly's weariness prompts Nancy to escort her back to the warm embrace of her foster family.
As Joan delves deeper into the intricacies of diamond authentication, Boisie finds himself in the company of Hugo, his esteemed auctioneer, seeking his expertise to validate the painting for the IRA deal. Hugo, however, declines but offers a compromise: training a proxy to take his place.
Joan's anxiety reaches fever pitch following a confrontation with Tom, the undercover policeman, who presents her with a chilling sketch of her likeness and a dire warning—he knows of her involvement in the theft. In a bid to protect her, he offers a Faustian bargain: her cooperation in exchange for her safety.
That very night, Joan steals away to the warehouse, her heart heavy with resolve to end this nightmare by destroying the painting. But Boisie, ever vigilant, shadows her steps and intercepts her at the last moment. He lays bare the IRA deal, painting a dire picture of the consequences should he back down, leaving Joan with little choice but to acquiesce.
Dressed in the mantle of an auctioneer, Joan attends the fateful meeting with the IRA, her nerves on edge. Guided by one of their members, she meticulously examines the painting, her words weaving a convincing tale of authenticity that leaves no room for doubt. Thus, the duo navigates yet another treacherous turn in their tumultuous journey.
At the club where Boisie anxiously awaited his due, the IRA showed no mercy, withholding payment and menacingly ordering him to vacate the premises. In a parallel turn of events, the police descended upon the hotel room where Joan was meticulously verifying the authenticity of the painting, ultimately resulting in her arrest. Shackled and escorted to prison, Joan found herself in a predicament where Kelly's foster parents, mindful of her situation, advised her to sever all communication with Kelly while imprisoned, fearing it could only exacerbate her difficult circumstances.
