Park Chanyeol is a cold, ruthless businessman working for EXODUS Gold Partners, a major bond investment firm, and he has an axe to grind against the company SM Group. His philanthropic father was once SM's CEO, but he was charged with embezzlement after his death, leading to Chanyeol's mother committing suicide and all their family shares were transferred to Park Youngmin, Chanyeol's uncle who now runs the company. Min-ho believes that his father was framed, and he's determined to get revenge by wresting control of SM. He wants that to be his last living act, since his doctor diagnosed him with dilated cardiomyopathy (the same condition that killed his father) and one more month left to live; only a donor heart would save him, though finding a match is unlikely given his rare blood type.

As he butts heads with his uncle, Chanyeol comes across Byun Baekhyun, the daughter of his father's former secretary and who now works herself at Hermia as Chairman Park's executive assistant. Baekhyun is happily engaged to Jung Daehyun, a detective, though unaware that her childhood friend and colleague  has loved her for years. After Daehyun has an altercation with Chanyeol when the latter tries to shut down the SM Cosmetics factory that employs his father Jung Kyung Ho and Lee Minhyuk's security guard father Lee Jung-gu, Chanyeol blackmails baekhyun into working for him instead.

Minhyuk is SM's legal affairs director, but has long resented doing Chairman Park's dirty work. When Daehyun's investigation into one of SM's skincare products being tampered reveals Minhyuk's involvement, Daehyun tells Minhyuk to confess or he'll arrest him. Soon after, Daehyun dies in an apparent hit-and-run and in a strange twist of fate, Chanyeol becomes the recipient of his heart and makes a full recovery. But Chanyeol begins to exhibit different personality traits and habits, ones similar to the deceased Daehyun's, and finds himself falling for Baekhyun.