Seven years ago, Jennie Kim was the "it-girl" with a dark secret. She dumped the love of her life, Lalisa Manobal, telling her she was just a "charity project." Lisa left Korea with a broken heart and a burning desire for revenge. Now, Lisa is back. She's the "Monarch of Manhattan," a tech billionaire who just bought half of Seoul. She's cold, she's ruthless, and she's the new partner for the struggling Kim Group. But Jennie isn't the girl she used to be. She's married to Kai, a clueless heir who treats her like a shiny doll. She lives in a "Gold Cage," serving tea and smiling for cameras while her father pulls the strings of a criminal empire. When Lisa and Jennie meet in a high-rise office, the air literally vibrates. Lisa wants to ruin Jennie. Jennie wants to save Lisa. But neither of them knows the truth about the "Black Contract" signed seven years ago.

Jennie is an assistant at Manoban Inc. She can't stand her job or her boss, Yang Hyunsuk, but she needs the money. One day she's finally had enough and ends up ranting in the elevator to a stranger who ends up to be no other than Lalisa Manoban. They run into each other several times after and Jennie begins having a thing with the sexy CEO. Things begin to turn when they both begin to develop feelings for each other.