Myeong-jun accepts his ex-wife Hye-eun's proposal to kidnap an 11-year-old girl named Ro-hee to pay for his daughter's hospital bills. En route to execute his plan, someone collapses before his car, which turns out to be Ro-hee. He takes her home, but she can't remember anything when she wakes up. Myeong-jun claims to be her dad and contacts her parents for the ransom, but they can't be reached.

Myeong-jun finds out that Ro-hee's parents have been murdered. He can no longer demand ransom or bring Ro-hee back to her home. As he heads to Ro-hee's home, a suspicious figure approaches Ro-hee who is home alone. Meanwhile, Sang-yun, the detective in charge of the case of the murdered hospital director and his wife, learns of their daughter's kidnapping and begins tracing Myeong-jun's footsteps.

Ro-hee finds out that Myeong-jun is not her dad but a kidnapper. Myeong-jun decides to take Ro-hee to the police station and turn himself in. Right then, Ro-hee regains a part of her memory and is left in shock. Meanwhile, Sang-yun discovers something about Myeong-jun's past.

Myeong-jun and Ro-hee stay the night at Hye-eun's house, the mastermind behind the kidnapping. Ro-hee is in disbelief when she discovers Myeong-jun's decision to take all the blame for kidnapping her. Ro-hee remains suspicious of Hye-eun and, in the end, finds out the real reason for Hye-eun leaving Myeong-jun and Hee-ae. Meanwhile, Sang-yun finally faces Myeong-jun after an unyielding pursuit.

Myeong-jun and Ro-hee find themselves in Choi Jin-tae's villa. Myeong-jun learns of "The Genius Child Project," a brain experiment Ro-hee was a subject in. Dr. Mo attempts to separate Ro-hee and Myeong-jun. Meanwhile, Sang-yun digs into a case from 30 years ago to catch the culprit of the hospital director and his wife's murder case and hears an unexpected name from a witness of a past case.