The climactic episode of "Master of the House," titled "The Offer," opens with Phupat confronting Kaimook as she securely latches the door to the Thevasatitpaisarn mansion. With suspicion heavy in his voice, Phupat inquires whether Kaimook is the one who extinguished Roongroj's life, prompting Kaimook to burst into mocking laughter.
The narrative then takes us on a journey five years into the past, where Kaimook first stepped into the Thevasatitpaisarn family's service as a maid. On her first day, Padcha and Araya strip the maids, including Kaimook, of their dignity, demanding nudity as a means of control. As days unfold, Kaimook uncovers the family's deeply disturbing nature. She witnesses Mavin indulging in sexual liaisons with Kaew and discovers Phupat's dependency on drugs. Furthermore, she learns of the heinous acts committed against her fellow maid, Dao, who was sexually assaulted by Roongroj.
To distract herself from the grim realities around her, Kaimook expresses her fascination with butterflies and moths, a hobby that piques Roongroj's interest. He becomes engrossed in collecting them for her, unbeknownst to him the extent of his looming downfall.
Tragedy strikes when Kaimook learns of Dao's suicide, and she is subsequently appointed as Roongroj's personal servant. One fateful day, he summons her to his greenhouse and violates her. Kaimook, initially terror-struck, eventually succumbs to the belief that this is her destiny and continues her sexual relationship with Roongroj.
Kaimook's manipulation of Roongroj begins to take shape over the years. She fosters a bond with him, promising to bear him an heir when he confesses his despair over Phupat and Mavin's incapabilities. This pledge leads Roongroj to name Kaimook as his successor and bestow all his assets upon the child she would eventually bear.
On the eve of his birthday, Kaimook subtly spikes Roongroj's tea with Phupat's illicit drugs. As Phupat storms in to confront his father, Kaimook slips into Mavin's room, handing him a forged termination letter designed to incite rage. Enraged, Mavin rushes to confront Roongroj, who, under the influence of the drugs, hallucinates butterflies pushing him off the balcony, resulting in his tragic demise.
Upon uncovering the truth about Kaimook, present-day Phupat is thrown into a whirlwind of anger and accusations. He learns of her devious plot, blaming her not only for the demise of his father but also for manipulating him into murdering Mavin. Kaimook, unrepentant, counters by insisting that Phupat's actions were solely his own, further gaslighting him by falsely claiming he had also poisoned Roongroj.
To drive her point home, Kaimook produces a video recorded on the boat, showing Phupat choking and pushing Mavin off the vessel. She reveals that Joke had filmed the entire harrowing incident, emphasizing that the household servants, tired of their masters' mistreatment, had united against them.
Phupat's rage reaches its boiling point, and he lunges for Kaimook's neck, intent on strangling her. However, the servants intervene at this crucial moment, capturing on film Phupat's attempted assault on his late father's wife. They leverage this footage, threatening to tarnish the Thevasatitpaisarn family's reputation unless Phupat desists.
Weeks pass, and Phupat finds himself drowning his sorrows in a local bar. On the television screen, he spots Padcha being interviewed by reporters, the news of his crimes—spread by Kaimook's cunning plan—painting him as a monster. Padcha, feigning ignorance, distances herself from Phupat's actions and flees to New York, where she tries in vain to reconnect with Kita, who ignores her desperate pleas.
Elsewhere, Araya auditions for a new acting role, her tears mingling with memories of Shutter, who failed to survive the heart transplant. Meanwhile, Phupat, leaving the bar, is viciously stabbed and abandoned to his fate by ruthless robbers. With Phupat's near-fatal encounter, the entire Thevasatitpaisarn family crumbles, a victim of Kaimook's treachery and the servants' Collective betrayal.
What becomes of the servants, and how does the saga of "Master of the House" ultimately conclude? According to Roongroj's testament, his entire fortune, encompassing a full ownership of Theva Gems, is bestowed upon Kaimook. In a poignant act of reversal, the servants gather for a group photograph within the mansion, swapping out the portrait of the Thevasatitpaisarn family with one featuring all the maids and male servants, symbolizing a shift in power and place.
The season one finale of "Master of the House" unfolds with a poignant scene: the maids rejoice at the very dining table that once hosted the Thevasatitpaisarn family. Kaimook, atop the table, dances with abandon, while the remainder of the servants join in, their steps echoing a triumphant celebration of their newfound agency and freedom.
