Episode 4 of "When the Phone Rings" kicks off by transporting us back to the poignant moment when Sa-eon receives a phone call from the nursing home, informing him about his father-in-law's condition. In a gesture of immediate support, the president offers him the use of his official vehicle to expedite his journey. We then cut back to Sa-eon, who finds Hee-joo by the roadside, tears streaming down her face. With discretion in mind, he asks the officers to keep the situation confidential and vows to swing by the station later to provide a detailed statement. He even playfully agrees to pose for a picture with the officer, lightening the somber atmosphere.
Sa-eon gently guides Hee-joo to his car, allowing her the space to grieve freely. He teases her about her less-than-picture-perfect appearance when she cries, yet his words are tinged with affection and understanding. He reassures her that he will secure a safe haven for her father.
Switching gears, he reminds her of their dinner plans with his parents. Instead of escorting her home, he directs her to the hotel where he's meeting his folks and secures a room for her to unwind. Prior to this, he engages her in conversation, subtly steering the topic towards the kidnapper. He confesses his dilemma: as the victim, he can't file a police report without drawing suspicion to himself. Mentioning Hee-joo could unravel a chain of investigations leading back to her. He inquires if there's something she's holding back, and she remains noncommittal. He senses her hesitation but respects her boundaries, vowing not to pry.
Attending the dinner solo, Sa-eon finds himself locked in a heated exchange with his father. His dad harbors hopes that Sa-eon will abandon his current job to support him in his forthcoming presidential campaign. Yet, Sa-eon stands firm in his resolve, unwilling to shadow his father's ambitions.
In the confines of the hotel room, Hee-joo meticulously cleanses her face and savors the snacks thoughtfully ordered by Sa-eon. She drifts into a peaceful slumber and only emerges later to join them for dinner. Understandably, her in-laws are displeased by her tardiness, despite Sa-eon's explanation that Hee-joo had been unwell. Ui-hyong, unable to resist voicing his discontent, begins a rant about Hee-joo's muteness and her failure to fulfill her duties. He contends that II-Kyeong deceived them, leaving them saddled with an unproductive daughter-in-law.
Sa-eon rises abruptly, instructing the hotel staff to retrieve the camera belonging to the paparazzi camping outside due to his father's influence. He asserts firmly that neither threats nor questionable marketing tactics will coerce him into abandoning his career to assist his father. He effectively deflates Ui-hyong's ego by revealing that Ui-hyong's achievements are solely due to riding on his father's coattails. Unlike Ui-hyong, Sa-eon vows not to exploit his father's legacy, clarifying that he has forged his own path outside of his father's shadow. With that, he takes Hee-joo's hand and they depart, leaving Ui-hyong's vitriol behind. Ui-hyong, incensed, throws a wine glass at them, but Sa-eon swiftly shields Hee-joo from harm. Inside the elevator, he urges her to ignore his father's disparaging words, reminding her that they are unworthy of her attention. Hee-joo is deeply touched and startled by his protectiveness. She attempts to withdraw her hand, but Sa-eon holds her firmly, refusing to let go.
Elsewhere, You-ri encounters Sang-woo at one of her favorite local eateries. Sang-woo inquiries about Sa-eon, prompting You-ri to recount how Sa-eon served as a beacon of inspiration for her when she was just starting out. She reveals that Sa-eon is now married to the influential daughter of a newspaper conglomerate. Curiosity piqued, she asks if Hee-joo is Sang-woo's secret crush, leaving him momentarily speechless with astonishment.
Sa-eon and Hee-joo return home, where Sa-eon receives a call from Do-jae, informing him that the kidnapper's recent threat employed fake teeth and animal blood. Sa-eon, surprised, asks Do-jae for another favor. Inside the house, Hee-joo ponders over the kidnapper's words and briefly considers discarding her phone but reconsiders when Sa-eon offers to take out the trash, sweetening an already tense evening with a gesture of care and consideration.
As they tussle over the garbage bag, Hee-joo's phone rings, interrupting the chaos. It's a call from her colleagues, who shower her with well-wishes for her upcoming interview. Sa-eon joins in, offering his own blessings and inquiring about her plans post-employment. Worried about potential familial disapproval, Hee-joo pours out her concerns to Sa-eon, who urges her to shed her obedience and disregard the opinions of others. With that, he retreats to his room, where a message from Do-jae awaits, informing him about a potential new nursing home for his father-in-law.
The following morning marks Sa-eon's unprecedented tardiness to work. Upon arriving, Do-jae promptly announces that they are inching closer to identifying the kidnapper's gender through speech pattern analysis. Sa-eon brushes it off, insisting that his only priority is unmasking the culprit. Do-jae then shifts the conversation to Sang-woo, reveling in the latter's fascination with arson and bombing cases and hinting at his upcoming appearance on You-ri's show. This piques Sa-eon's curiosity.
Young-woo's report soon follows, heralding the commencement of the sign language interpreter interview. Initially deciding to skip it and observe from his office, Sa-eon's resolve wavers upon witnessing Hee-joo's performance. He summons her out, criticizing her for being overly aligned with the trial video and subjecting her to multiple rounds with different clips. Each time, Hee-joo aces the test, prompting Sa-eon to inquire about her exceptional ability. She reveals that she once studied his videos extensively, to the point of predicting his next words based on his lip movements. Admitting to her past infatuation, Hee-joo leaves Sa-eon flustered yet composed.
Finally, he tasks her with interpreting a document on the spot, narrating a tale of a distant couple deeply in love yet reluctant to confess their feelings. He ponders whether honesty from the outset would have altered their fate, sparing them the game of mind games. As Hee-joo flawlessly interprets, Sa-eon exits the room, his thoughts drifting back to their conversation from the previous night, wondering about Hee-joo's true intentions.
Elsewhere, Hong I-na finally returns to the country. Subsequently, Hee-joo receives a notification regarding her father's transfer and proceeds to visit him at his new residence. Her heart is warmed when her father reveals that Sa-eon assisted him in moving and even bought him new socks. She confesses her inability to fathom Sa-eon's intentions, as he alternates between sweetness and kindness, and coldness and distance.
At the office, Sa-eon admits to Young-woo that he was impressed by Hee-joo's diligence. A flashback takes us to their childhood, where they crossed paths at a dinner party. While Hee-joo was being bossed around by her mother, Sa-eon rebelled against his own mother's expectations by refusing to eat fish. Ultimately, he offered his portion to Hee-joo, who loved it, but her mother denied her more. Since then, he has harbored feelings for her. As he relishes these memories, he receives a message from Hee-joo, thanking him for taking care of her father.
Later in the evening, Hee-joo learns that her sister has returned to South Korea. This triggers a recollection of the night her mother asked her to take I-na's place. She remembers how Sa-eon handed her a wedding ring and entrusted her to safeguard it until the rightful owner appeared. After some contemplation, she reverses her decision and opts to keep the black phone.
Meanwhile, on his way home, Sa-eon calls You-ri to inquire about Sang-woo. You-ri, being notoriously talkative, spills the beans that Sang-woo once lived in an orphanage, prompting Sa-eon to surmise that it was the Nuri Dream Centre. Following his conversation with You-ri, the kidnapper (revealed to be Hee-joo) calls again.
This time, she addresses Sa-eon's question about what he stands to gain by abandoning Hee-joo. Hee-joo raises the subject of her sister's return and inquiries whether Sa-eon would be content with welcoming I-na back and divorcing her.
However, Sa-eon clarifies that he and I-na had reached an agreement on the eve of the wedding, a pact that eternally bars him from marrying her. Before Hee-joo can delve deeper with her inquiries, he abruptly ends the call. Upon arriving at the house, he commends Hee-joo for her impressive interview performance and reveals his intention to attend the Chungwoon Daily News anniversary event the following day. Hee-joo assumes his attendance is solely to catch a glimpse of I-na.
The next day, tension escalates into a full-fledged spat between Kyu-jin and Yeon-hui at the salon, just before the event is set to commence. The event itself proceeds smoothly, with Ui-hyong putting forth a concerted effort to portray himself as diligently striving to persuade Sa-eon to join his ranks. Chairman II-kyeong expresses concern that the presidential election might falter without Sa-eon's involvement. In a separate incident, Yeon-ju reproaches Hee-joo for revealing the truth about her biological father to Sa-eon.
While in the ladies' room, Hee-joo inadvertently eavesdrops on a conversation where the girls maliciously gossip about her while extolling the virtues of I-na, who fails to appear. She returns to the venue, her heart heavy, to find Sa-eon engaged in a discourse with those same malicious women. Disheartened, Hee-joo grabs a glass of wine and retreats to the rooftop.
At 10 pm, she dials Sa-eon's number, her voice tinged with the accusation of a kidnapper's. He hesitates before answering. Once connected, she inquiries about his emotions when I-na deserted him. He responds coolly, stating there was no significant impact. Hee-joo, feeling insulted, launches into a tirade about being merely a substitute, devoid of social acumen. She describes herself as a mere adjunct to I-na's allure, blinded by the trappings of luxury.
Sa-eon corrects her perception, stepping in to defend her honor, requesting 406 (presumably a reference to Hee-joo in a context not fully explained here) refrain from speaking ill of his wife. Unbeknownst to Hee-joo, Sa-eon is en route to the rooftop, intent on delivering a coat to her. His words flow with affection, painting a loving picture of Hee-joo that astounds her. He confesses that upon their first encounter, she was the solitary soul who brought him tranquility, her silence a soothing balm.
Hee-joo's tears stream down her cheeks as she inquisitively wails, questioning why he subjected her to such harsh treatment. The elevator doors chime open, revealing Sa-eon stepping out to find her engrossed in a conversation on the sleek black phone. The epilogue unveils a pivotal moment: as he fulfills his obligation to the policeman by giving his statement and adhering to his promise to snap a photograph, Sa-eon uncovers Hee-joo's hidden truth.
He is left stunned when the police officer recounts the desperate, piercing screams of Hee-joo, begging them to halt the vehicle. He requests the dashcam footage, and for the first time, he is astounded to hear Hee-joo's voice. Initially, Sa-eon's anger seethes as he listens to the recording, but a sudden calm envelops him, sparking an intense internal reckoning where he begins to question everything he thought he knew.
