Gu Seo Jin is a third-generation chaebol who runs the theme park Wonder Land. He seemingly has everything — looks, brains, and fortune. But a traumatic incident in his childhood resulted in Seo Jin having a split personality — one is a cold, ruthless man, while the other is the polar opposite, someone kind and gentle. Because of this, he vows never to date or marry. Seo Jin wants to get rid of the circus show at Wonder Land due to low ticket sales and high overhead costs, but he butts heads with circus master Jang Ha Na. Ha Na insists on saving the failing circus and dreams of revamping it back to its former glory. She soon finds herself falling for both of Seo Jin's personalities. Based on Lee Chung Ho's webtoon "Dr. Jekyll Is Mr. Hyde".