The episode kicks off with William "The Duke" Wellington (Stuart Martin) and Eliza Scarlet (Kate Phillips), cloaked in secrecy under the guises of Dr. and Mrs. Evans, delving into their undercover mission. As they dine, he whispers to her that patrons of the elegant restaurant have fallen prey to burglaries while indulging in their meals. Eliza's gaze drifts as an old acquaintance, Arabella Acaster (Sophie Robertson), ambles over, recounting a humorous anecdote about Eliza emerging from a muddy puddle, resembling a creature of the swamp. Arabella, the proprietor of Arabella's, adds a touch of intrigue to the evening.
Just as they step out of the restaurant, the duo stumbles upon a crime in progress. The Duke sprints after the fleeing suspect, leaving Eliza to confront Tibor (Stefan Vukic), who demands her brooch with a menacing grin. She retaliates by warning him of the police siege encircling the premises, yet he snatches her brooch and dashes away, leaving her angered and puzzled.
Returning to Arabella, The Duke reveals the police are probing into a series of jewel thefts reported by her restaurant's patrons. Eliza, unmasked as a private detective, concurs that the timing of the two robberies couldn't be mere coincidence. She posits that the first crime was a clever distraction, to which he nods in agreement, adding that the lavender peddler might be a cog in the criminal machinery.
Ivy (Cathy Belton) expresses admiration for Arabella's entrepreneurial spirit, to which Arabella responds by sharing the restaurant's history, once belonging to her late husband's family. She reveals her father was a jeweler, adding depth to her character.
The Duke enlightens Eliza, revealing that the lavender peddler and the robber were hired hands, aiming to create a diversion to steal her brooch. Determined to uncover the truth, she insists on accompanying him to identify Tibor. Upon reaching the tavern, he orders her to await his return in the carriage. Meanwhile, Detective Fitzroy (Evan McCabe) casually mentions his boxing training, adding a layer of unpredictability to the scene.
The tavern landlord (Igor Filipovic) feigns ignorance when questioned about Tibor, who slips away undetected. Eliza, sensing an opportunity, bursts out of the carriage just as Tibor passes by, catching a glimpse of Arabella Acaster's business card, inscribed with "Lady Blue Dress Spilla," tucked safely in his pocket. The stakes are raised, and the mystery deepens.
Eliza delves into the origins of "Spilla," an Italian term signifying "Brooch," sparking her curiosity. Tibor, brandishing a tattoo of Budapest's infamous Vac Prison on his forearm, claims serendipitous discovery of a mysterious business card on the city streets. The Duke, with an air of menace, warns Tibor of a swift return to his Hungarian cell if he fails to disclose the provenance of a cryptic note.
As Eliza enters the restaurant, she witnesses Arabella dismissing Grace (played by Tafline Steen) from her duties. Arabella then embarks on a guided tour of the eatery, showcasing its diverse workforce hailing from various corners of the globe. Among them, she highlights Paolo, their talented pastry chef, and Enzo Moretti (Nikola Stankovic), an Italian waiter, just as The Duke strides in. He reveals to Eliza that Enzo is allegedly colluding with a street urchin to prey upon unsuspecting patrons.
Grace confides in Eliza about Arabella's financial woes, leading to layoffs due to insufficient funds. Eliza ponders if there might be a way to lend assistance, recalling Grace's revelation about Arabella stashing a loan in her safe, a thick wad of cash.
Eliza visits Mrs. Herbert (Abigail Thaw), relating her background as a Hertfordshire native, along with her husband, an MP representing Chalfont St. Giles. She expresses hope to catch up with Arabella, but Mrs. Herbert reveals a somber tale: Arabella's husband passed away, leaving behind a mountain of debts. Eliza mentions Arabella's claim of financial support, which Mrs. Herbert promptly refutes, adding that Arabella's loan applications were unanimously denied.
Eliza tails Arabella to a clandestine meeting with the enigmatic Lavender Woman (Sam Bell). Summoning a police officer to fetch The Duke, they infiltrate the venue to find Arabella serving meals to the homeless. Confronted with the Lavender Woman's criminal past, Arabella feigns ignorance. Eliza confronts her, citing a conversation about her supposedly 'thriving business' with Arabella's mother. Arabella admits her financial strife but insists on maintaining her pride. The Duke interventions, counseling Eliza to let bygones be bygones.
Eliza confesses to allowing her personal emotions to weave their way into her professional endeavors. She would deliberately provoke conflicts with Arabella, fueled by her frustration at not feeling accepted. Her intention was for Arabella and her circle to dislike her actions, not the child she once was, a distinction Ivy earnestly tried to impress upon her, assuring her that those girls would never approve of any course she chose. Meanwhile, Eliza's Victoria sponge cake fell short of her expectations.
While eagerly awaiting Arabella in her office, Eliza's impatience led her to pick the lock of her safe. Inside, she uncovered an invoice from R. Bennett's Pawnbrokers. Arabella, entering her office moments later, found Eliza already absent, leaving her to ponder the discovery.
Fitzroy informs The Duke that Enzo collaborates with his uncle, Frankie, who had been entangled in a theft inquiry. Inquisitive, The Duke inquires if Frankie might have returned to London. Fitzroy confirms that Frankie's former workshop is operational once more. Storming into the workshop, The Duke forces open the door and they return to the police station with a treasure trove of evidence.
The Duke updates Eliza on Enzo and Frankie's workshop, returning her mother's brooch to her. She reveals that Arabella has sold six pieces of jewelry, totaling 300 pounds, over the past three months. However, The Duke notes that Arabella had proof of ownership for each item. Eliza points out that a heart-shaped sapphire ring listed was among the items found in Arabella's safe. He speculates that perhaps Arabella owned two similar rings. She wonders aloud why he refuses to acknowledge the information as incriminating evidence. He reassures her that his decisions are grounded in understanding motives, before departing. As she absentmindedly runs her finger over her mother's brooch, a gem loosens from its setting, catching her by surprise.
The Duke and Fitzroy engage in a discourse about Frankie's former workplace, a jewelry establishment belonging to an old-country family. When Eliza seeks counsel from Solomon, he laments about his declining vision. She reassures him, insisting that his eyesight remains sharp and that he is a man of considerable wealth. Solomon eventually concedes, on the condition that Eliza purchases two items from him. He reveals to her that the brooch in question is a counterfeit, with its red gems being composed of Murano glass rather than authentic rubies.
Upon arriving at the jewelry store where Frankie once toiled, the Duke and Fitzroy find it shuttered. They are about to depart when Fitzroy catches sight of a brooch resembling Eliza's. The Duke instructs him to procure a bolt cutter. Fitzroy queries whether a search warrant is necessary for lawful entry. The Duke, however, pretends to hear a woman's cries for help emanating from within the store.
Eliza confides in Arabella, revealing her plan to sell replicas of her genuine jewelry. Arabella urges her to wait until the patrons are seated. Eliza agrees to await in her office, where she unexpectedly encounters Grace, who is carrying a bag filled with jewelry.
The Duke identifies the brooch as Eliza's. Fitzroy notes that Enzo and Frankie hailed from Murano, a place renowned for its glass that mimics precious gems. Both men conclude that the jeweler is linked to a criminal syndicate. The jeweler's modus operandi involves substituting the real jewelry with replicas before presenting it to the customer.
Eliza inquisitively turns to Grace, seeking the identity of the one who commanded her to pilfer the precious jewels. With a trembling voice, Grace reveals that Enzo had coerced her with the grim threat of causing harm to Arabella should she refuse. The Duke, concerned and resolute, informs Mrs. Herbert of his desire to converse with Arabella. Mrs. Herbert, her face pale with worry, responds that Arabella is currently absent, only to hurry back indoors where a harrowing scene unfolds – Enzo holds her maid captive, a gleaming knife at her throat.
As Enzo escalates his threat towards Mrs. Herbert, the Duke arrives on the scene with swift determination. With a powerful punch to Enzo's face, he intervenes, rescuing Mrs. Herbert from imminent danger. Arabella, eyes wide with fear, dashes to her mother's side, seeking solace.
It transpires that Arabella, driven by desperation, had sold her own jewelry and donned replicas to maintain the illusion of affluence among her clientele. Moved by her plight, the Duke refrains from laying charges, understanding that her actions were solely motivated by her desire to safeguard her mother's well-being. Arabella, her voice tinged with bitterness, recalls Eliza's past dismissals of her father, acknowledging her own jealousy towards Eliza and revealing that her father had shown little interest in her.
Later, Ivy, with a warm smile, instructs Eliza in the art of crafting a Victoria sponge cake, a gesture intended to brighten her spirits. Eliza, carrying her heartfelt creation to the Duke, finds her cake overshadowed by Arabella's exquisite pastries. In a moment of kindness, Arabella returns Eliza's necklace, extending an invitation to dinner. However, Eliza, her heart heavy with unresolved emotions, declines, as the episode draws to a poignant close.
