Episode 4 of "Cinderella at 2am" unfolds with a poignant prologue, as Ju-won and Yoon-seo, their bond severed by a mutual decision to part ways, find themselves nostalgically revisiting memories of their time together. At the office, they cautiously navigate each other's presence, striving to avoid awkward encounters. However, Yoon-seo's tranquility is disrupted by a string of enigmatic texts from an unfamiliar number, declaring an inability to forget her. Initially dismissing the notion that Ju-won could be the culprit, her suspicions ignite when she discovers he possesses two mobile phones.
Convinced the messages stem from Ju-won, Yoon-seo confronts him, only to be mortified when the truth reveals itself: the second phone belongs to the company as a test sample. Embarrassed yet determined, she confides in I-rae about the mysterious texter, and together they embark on a quest to uncover the sender's identity. Their call leads to a mundane revelation—a simple case of mistaken identity.
Meanwhile, Yoon-seo and Ji-suk mend fences, with Ji-suk vowing to rectify his wrongs by apologizing to his classmate and embracing a newfound resolve to prepare for a competitive exam, albeit without a clear vision of its destination. Their chance encounter with Ju-won on the way home serves as a stark reminder of Yoon-seo and Ju-won's recent separation. After Ji-suk's departure, Ju-won, mindful of Yoon-seo's discomfort, offers to relocate offices.
Elsewhere, Si-won's world is turned upside down by the unexpected return of his wife from France. Having grown accustomed to solitude, he finds himself at odds with the changes wrought by her presence, longing for the day she would depart. A flashback transports us to the beginnings of their arranged marriage, sparked by a chance blind date on a flight to Paris. Their union, a study in contrasts, now stands on shaky ground.
As Yoon-seo gears up for a business trip, the relentless texts from the unknown number persist, fueling her frustration. She confronts the sender, unleashing her emotions about the struggles of navigating a breakup amidst the confusion of these unsolicited messages. The veil is lifted, revealing the anonymous texter to be a painter, his interest in Yoon-seo palpable through every word.
On their journey to the pivotal business meeting, an unforeseen mishap strikes Yoon-seo's colleague, whose pristine new car succumbs to an accident, leaving Ju-won to swiftly intervene and offer them a lift. The subsequent car ride, however, takes an unexpected turn as Ju-won's car's Bluetooth inadvertently pairs with Yoon-seo's phone, sparking curiosity and whispers among their fellow passengers. Matters only worsen when, amidst the tension, Ju-won slips and affectionately addresses Yoon-seo as "honey," adding a layer of awkwardness to the already charged atmosphere.
Despite these hiccups, they eventually reach the meeting's destination, where Yoon-seo finds herself beaming with pride at Ju-won's professional strides.
Elsewhere, Si-won's world turns upside down upon learning that his wife intends to extend her stay in Korea, effectively curtailing his cherished independence.
At the opening ceremony's grand stage, a revelation strikes Yoon-seo like lightning: the realization that their dual careers cannot coexist harmoniously. With heavy heart, she confides in Ju-won that evening, her intention to resign from her post. This news sends Ju-won rushing home, where he implores his mother to facilitate his departure overseas. To his surprise, he learns that he is destined to fill Si-won's shoes, as his brother and sister-in-law embark on an expansion venture, leaving him to shoulder new responsibilities.
After a passionate clash with his mother, Ju-won finds solace only in Yoon-seo's embrace, confessing his utter helplessness. Yet, fate seems to have other plans as Yoon-seo's colleagues unexpectedly stumble upon their intimate moment, just as I-rae arrives on the scene, his exclamation echoing through the air, wondering aloud if the two have reignited their once-lost spark.
