In the riveting fourth episode of "When the Phone Rings," the emotional turmoil within Hee-Joo reaches a boiling point, and the layers of deception that have enveloped her life begin to unravel. The episode opens with a heart-wrenching scene where Hee-Joo, overwhelmed by the pain she's endured, sits in the car with Sa-Eon, crying silently. Her tears, a stark contrast to her perceived muteness, speak volumes about the anguish she's been harboring.
Meanwhile, Yu-Ri and Sang-Woo's paths cross again, leading to a casual dinner at a local restaurant. Their conversation takes a personal turn when Yu-Ri observes that Hee-Joo was clearly Sang-Woo's first love. This revelation adds another layer to the complex relationships that are beginning to surface. As they discuss Sa-Eon, Yu-Ri recounts his strict yet guiding presence in her career, highlighting the distance that grew between them after his departure for the presidential office and subsequent marriage.
The tension escalates when Sa-Eon and Hee-Joo are supposed to meet his parents for dinner. Noticing Hee-Joo's tear-streaked face, Sa-Eon gives her the option to come later to compose herself. However, the dinner is fraught with tension from the start, with Sa-Eon's father being distant and dismissive, even throwing cruel jabs at Hee-Joo for being a "substitute" daughter-in-law. The arrival of a photographer to document Sa-Eon's potential political rise adds an uncomfortable layer to the already tense atmosphere.
Unable to tolerate his father's insults, Sa-Eon finally defends Hee-Joo, leading to their abrupt dismissal from the meal. Later, alone with Hee-Joo, Sa-Eon angrily questions why she always endures everything without standing up for herself. However, as expected, she doesn't—or can't—answer him, leaving the question hanging in the air.
In a moment of determination, Hee-Joo decides to dispose of the mysterious phone that has brought her nothing but trouble. However, Sa-Eon catches her in the act, and shortly after, she receives an encouraging call from her colleagues wishing her luck on her upcoming interview for the interpreter position for the president's spokesperson. This call serves as a reminder of the professional life she's been trying to build amidst the chaos.
Sa-Eon's curiosity about Sang-Woo deepens as he learns that Sang-Woo runs an online channel dedicated to solving cold cases. This revelation sparks his interest and adds another piece to the puzzle of Sang-Woo's mysterious past.
During the interpreter interview, Sa-Eon monitors the process through his computer. He is surprised by Hee-Joo's sharp and precise performance, often finishing his sentences faster than he could himself. Intrigued, he decides to test her directly by challenging her to interpret him in real-time as he reads a passage aloud. The topic of "couple's day" makes the situation uncomfortably personal, but her flawless interpretation impresses everyone present. This leads his colleagues to place bets on whether Sa-Eon has feelings for her, and in a rare moment of honesty, Sa-Eon admits to his assistant that he does.
The episode takes a poignant turn with a flashback to Sa-Eon's childhood, showing his strained relationship with his father and the neglect he faced. In a touching memory, he secretly helps Hee-Joo when she's mistreated by her family during a visit. This act of kindness solidifies his desire to protect her, a sentiment that carries into the present.
Hee-Joo comes across an Instagram post from her sister, In-A, revealing she's back in Seoul. As she awaits another call from the "kidnapper," Sa-Eon speaks with Yu-Ri about Sang-Woo, learning that Sang-Woo grew up in the same orphanage linked to a mysterious photo. However, their conversation is cut short when Sa-Eon abruptly ends the call.
In another tense phone call, Hee-Joo tells the "kidnapper" (unbeknownst to her, Sa-Eon himself) that she wants a divorce because In-A is returning. Sa-Eon counters by revealing that he and In-A made a pact long ago to never marry, rendering the blackmail pointless. Shocked, Hee-Joo ends the call just as Sa-Eon arrives home. Surprisingly, he apologizes to her for underestimating her capabilities during the interview and praises her skills.
The next day, Sa-Eon and Hee-Joo are expected to attend the anniversary celebration of Chungwoon Daily News, hosted by her stepfather. At the event, tensions flare when Hee-Joo's mother scolds her for moving her biological father to a different nursing home, fearing the chairman's wrath. Amid this family drama, Hee-Joo sneaks away to the roof of the building, feeling overwhelmed. After a few drinks, she calls Sa-Eon and confronts him about how he felt on their wedding day, knowing his bride had been swapped. Her self-deprecating rant catches him off guard, though he counters every claim with sharp retorts.
As their conversation unfolds, Sa-Eon realizes she's on the roof and rushes to find her. There, he sees her precariously standing on a bench near the edge, phone in hand. In the episode's epilogue, Sa-Eon comes across dashcam footage from a police car showing Hee-Joo screaming during an earlier car ride. Realizing she's been lying about being mute, his frustration grows. It becomes evident that he suspected her secret even before the interview, which explains why he subtly tested her ability to speak.
This episode of "When the Phone Rings" is a masterclass in emotional storytelling, peeling back the layers of Hee-Joo's pain and Sa-Eon's protective stance. The performances are raw and captivating, and the plot twists keep the audience guessing, making this episode a pivotal turning point in the series.