As the curtains part on the inaugural episode of "Stags," two tunnel guards, Alexandre Cuny and Diego Santos, meticulously inspect the tunnel, confirming that the minefield and power systems have been restored. Tragedy strikes as one guard sustains an injury, leaving his compatriot to valiantly fend for himself, his cries for assistance echoing through the darkness.
Three months prior, in a scene that foreshadows the adventure ahead, Stu (played by Nico Mirallegro) confidently informs Ryan (Corin Silva) and Ant (Charlie Cooper) of his plan to pinpoint the elusive diamond and extricate the ring. Now, panic sets in as he cannot locate the precious band. Meanwhile, Kai (Jojo Macari) phones Ryan amidst Stu's relentless self-recrimination for misplacing the ring. Ryan endeavors to soothe Stu, whose fortune takes a sudden turn when he discovers the ring mere moments later. Soon, they embark on a plane bound for South America, their destination: an unforgettable stag party.
Sam (Holli Dempsey)'s call checking in on Stu is abruptly terminated as he is overtaken by another wave of nausea. Ant seeks refuge in the bathroom alongside Ryan and Stu, escaping the incessant whining of Clem (Sophie Lenglinger). Ryan, nostalgic for their mischievous youth, vows that their worst behaviors will be welcomed—an edict that applies regardless of whether they're in Mexico or not. Ant stumbles upon Kai preparing to snort drugs, but he declines, mindful of his wife and children awaiting his return.
As revelry ensues, Ant engages in a heart-to-heart with Clem and Hugo (Paul Forman), probing whether they were ever an item. Their denial sparks laughter. Meanwhile, Ant's father, John (Cavan Clerkin), urges discretion upon the group. The arrival of Greg (Asim Chaudhry) ignites a chorus of his name, and they collectively head to a local pub. In a touching moment, Stu asks Greg's permission to call him 'dad,' overwhelmed with gratitude for becoming part of his family.
Later, in the bathroom, Stu attempts to coerce Ant into indulging in drugs, but Ant stands firm, prompting Stu to vomit once more. At the airport, anticipation mounts as they await gate opening. Stu's disappointment is palpable when he learns of Ryan's concealed stash of drugs. Ryan argues that small quantities often go unnoticed, and indeed, he sails through security unscathed. Hugo, however, is less than thrilled with their reckless gamble, his exasperation directed at Kai, whom he mocks as an 'enchanted donkey.'
Their concerns escalate when Greg suddenly succumbs to stomach troubles, collapsing and convulsing. They learn with a shock that Greg had ingested a balloon filled with cocaine, his survival deemed miraculous. Clem's curiosity piqued, she wonders why Greg had a different layover flight. The tranquil scene is shattered by the sudden appearance of police officers, who swiftly apprehend everyone present.
Clem reveals her profession as a medic, setting the scene as the men are ferried to a prison by watercraft. Hugo's confusion deepens upon discovering women among the inmates, prompting him to inquire about Clem's fate. Ant gripes about the lack of a judicial hearing, while Ryan physically assaults Greg, leaving the latter's surgical scar bleeding profusely. As they are convoyed towards the prison, one inmate,恐惧于被同囚认出， attempts escape, only to be brutalized by fellow prisoners. Stu, offering assistance, is met with Ryan's skepticism.
Suspicions mount that this is no ordinary penitentiary. A desperate escape attempt ends in tragedy when a landmine claims a life. John proposes to Kai that they confront the authorities and demand audience with the British Consulate. Once inside, Ryan refuses to assist Greg, sparking a debate with Ant who reminds him of their shared drug involvement, to which Ryan dismisses as different circumstances. Stu and Ant pursue him, with Stu pledging support, convincing Ryan to seek medical aid for Greg.
The interior of the prison reveals a shocking tableau. John and Kai devise a narrative for their impending confrontation with the governor, with John bitterly noting his presence is tied to Stu's impending marriage to Sam. They enter to confront Governor De Leon (Sebastian Galvez), only to find themselves facing him via video chat, a surprise twist. Hugo tends to Greg, griping about his actions, while children approach, peddling cash on behalf of Branco and Selma (Paulina Galvez). Branco (Oscar Foronda) and Selma offer a weekly 35% return on investments.
Greg places a call, triggering a message to Selma. Meanwhile, Stu, Ryan, and Ant search for the doctor, who draws a gun on Stu in a bid for money. The Doctor (Tony Corvillo) ushers them inside, uninterested in Greg's wounds. De Leon informs Kai and John they await remand until their case reaches a state judge, potentially years hence. He's indifferent to alerting the British Embassy, doubting its efficacy. John attempts to shift blame, but De Leon describes El Porco Negro as a self-sustaining ecosystem.
The video call terminates, and the Doctor pressures Stu and his companions to accept drugs. Stu tries to draw attention to Greg's injuries, but the Doctor instead shows them a brutal punishment in a bathroom, urging them to leave promptly.
Ant assaults him with a chair, sending him crashing to the ground unconscious. From the bathtub, the captive man's screams pierce the air, pleading for assistance. He reveals a harrowing tale—the doctor intended to harvest his organs. Upon being liberated, the man seizes the firearm and bolts from the chamber. Emergency responders swiftly arrive, whisking Greg away on a stretcher. Stu bumps into John and Kai, urging them to flee. John confesses his ignorance, offering no solutions.
They trail Greg to a more upscale section of the prison, where Selma awaits them with curiosity. She probes the depths of Greg's wealth, to which Stu can only offer uncertainty, citing Greg's private nature. Ryan spills the beans about Greg's attempted cocaine smuggling, prompting Selma to doubt his financial status. She warns them that procuring surgery within prison walls is a costly endeavor, hinting at a significant debt owed by a group of Brits—a staggering $200,000. John protests, dismissing it as madness, but Selma stands firm.
Hugo proposes they secure a bridging loan from Branco, only for Selma to reveal that Branco is her brother. As they depart, Kai receives a cryptic note from the embassy, alerting them to their dire predicament—a century-long sentence looming. John remains skeptical, believing it to be a fabrication. However, the embassy has arranged a cell for their confinement, which John views as a positive sign of their care. Meanwhile, the bathtub escapee seems to be keeping a wary eye on them.
Upon reaching their designated cell, they find Clem already there, awaiting them ominously. Branco steps forward, demanding a pair of functioning kidneys as repayment. The doctor informs him that Ant was the one who struck him, but Branco retorts with a gunshot to the doctor's head, demanding another kidney for his troubles. With chilling nonchalance, he inquires who will be next to take a dip in the bathtub.
