Episode 3 of The Fiery Priest Season 2 kicks off with an evocative flashback. Prosecutor Park Kyung-sun is privy to Father Michael Kim Hae-il's grave illness, but there's a catch: Hae-il will only receive treatment if she assists him in unraveling a complex case. In the thick of the action, Heidi, an undercover police officer, introduces herself as Detective Gu Ja-yeon from the Busan Drug Investigation Unit. Misidentifying Hae-il and Detective Gu Dae-yeong as hoodlums, she apprehends them both.
Hong-sik, having come to terms with the Gudam disaster, issues a grim ultimatum to Boss Park: one blunder equals one life, resulting in the grim demise of one of Park's subordinates. Meanwhile, Ja-yeon's drug dealer beau, Sang-man, alerts them to Hae-il's arrest, prompting Hong-sik to reiterate his warning to Boss Park to tidy up the mess. Desperation sets in as Boss Park reaches out to Prosecutor Nam Du-heon, who, in turn, tasks Captain Lee of the Uma Violent Crimes Unit with drawing out Ja-yeon's team.
The Busan squad escorts Hae-il, Gu, and Fire Eel's gang to an abandoned bathhouse serving as their makeshift headquarters. Although the Busan officers eventually verify Hae-il and Gu's identities, they refuse to let them collaborate on the investigation. Even willing to be incarcerated alongside Fire Eel to uncover more, Hae-il and Gu find themselves booted out by Ja-yeon.
Sang-man finds himself entangled in a precarious situation, unknowingly dating an undercover cop. Hong-sik's frustration overflows as he confronts a fresh wave of problems on the very first day, instructing Boss Park to eliminate both Fire Eel and Sang-man. Elsewhere, Gozhaev, who had been occupied fixing a car, picks up Hae-il and Gu. To their astonishment, he is already au courant with the abandoned bathhouse's significance. As they deliberate on their next steps, they realize that Ja-yeon's unit is operating on slim information and has gone rogue.
Hae-il urges Kyung-sun to join her in Busan, but her fury ignites upon discovering that he's embarked on another case. She subsequently assigns Detective Gu and the conniving Gozhaev to stake out a bathhouse, much to the swindler's dismay. Their thoughts turn to Father Han and Sister Kim, only to witness them unexpectedly joining a theater troupe at the Uma church in Busan.
Ja-yeon's interrogations of Fire Eel yield no results, frustrating her. Her superior, Hyeon Woo-cheol, directs her to bring him to Nest 2, confident in their knowledge of Prosecutor Du-heon's corruption. Meanwhile, the prosecutor ponders the identities of Gu and Hae-il as he scrutinizes CCTV footage of Ja-yeon apprehending them. Unbeknownst to him, Hong-sik has already pinpointed the bathhouse by hacking into the police's phone locations.
Dean Lee catches Hae-il slipping into and out of the seminar unnoticed, yet lets him pass, respecting the priest's mentoring commitment. Hae-il leads Chae Do-u to a Uma neighborhood where elderly residents have been forsaken. They loathe sermonizing priests, as they lack both money and food. Neglected by the government, many have fallen prey to drug addiction.
The clergymen notice an elderly woman gathering boxes and lend her a hand by cleaning and cooking. They discover her frail lungs and Chae cunningly persuades Hae-il to serenade her, lifting her spirits. Though concerned, she reveals a silver lining: a new job at a nearby food factory. Hae-il presses some money into her hands, jesting that he's affluent.
In private, he charges Chae with keeping watch over the neighborhood. Instead of preaching about faith, he urges her to genuinely aid the residents and assure them they're not abandoned. Hong-sik's enigmatic deeds unfurl as it transpires he's become the chairman of Uma Nursing Home. He offers free accommodation and nourishment to the elderly, along with lucrative jobs at his factory for those willing to work. However, as he departs, he's repelled by the scent of aged skin.
He proceeds to encounter Du-heon, and amusement fills the air as they size each other up, each threatening something precious to the other. Assured of their mutual ambition and prowess, they reach a consensus to collaborate. However, trouble swiftly manifests in the guise of Kyung-sun, who encounters Hae-il in disguise as a runner. She uncovers Sang-yeon's predicament and is poised to incarcerate everyone involved. Her research reveals that Du-heon had previously convicted a drug dealer, boasting that Uma is now a drug-free haven.
Back in Gudam, Yo-han and Songsak are dismayed to learn that Father Han and Sister Kim have also absconded to Busan. Meanwhile, our clergymen arrive at the Uma church, but Hae-il swiftly catches wind of their presence. He confronts them alongside Gu, yet unexpectedly, the detective aligns with Han and Kim as they reprimand Hae-il for fleeing alone. Hae-il apologizes but insists that Han and Kim steer clear of danger.
Elsewhere, Hong-sik leads his men to a ship, unveiling it as a mobile base. Ja-yeong prepares to transport the Fire Eel, but Gozhaev notices that Hong-sik's men have discovered the bathhouse. As Gu and Hae-il rush after Ja-yeong, Gozhaev remains behind when the Uma Violent Crimes Unit arrives. They possess an arrest warrant for Woo-cheol and, if he resists, they have Du-heon's blessing to shoot.
In the vicinity, thugs ram into Ja-yeong's car and bear down on her. However, Hae-il and Gu arrive just in time, grinning as they prepare to overpower the assailants.
In the epilogue of The Fiery Priest Season 2 Episode 3, Yo-han's thuggish twin, Cho-rong, demands money. In the past, he had deceived Yo-han by stealing his money under the pretense of aiding their ill father. Songsak comes to Yo-han's rescue, punching Cho-rong. Boldened by Songsak's bravery, Yo-han intends to electrocute his brother but accidentally shocks Songsak instead.
