It turned out that Hwang Jung Eum was the child that was with Ji Sung in the basement.
On the episode of MBC "Kill Me Heal Me" broadcast on Feb. 18th at 10PM, Oh Ri Jin (played by Hwang Jung Eum) learned that she was the child that had been trapped with Cha Do Hyun (played by Ji Sung) in the basement.
On this day, Do Hyun's mother Shin Hwa Ran (played by Shim Hye Jin) went over to her husband who was recuperating from an illness. She said, "Actuality, I know. That you loved this woman very much. So I'm going to find this girl. I'm going to find her before Do Hyun and get rid of her."
The person that Shin Hwa Ran had pointed to in the picture was none other than Ri Jin as a kid. As it was revealed that the person trapped in the basement with Do Hyun was none other than Ri Jin, this foreshadowed troubles for Do Hyun and Ri Jin's future together.
Meanwhile, "Kill Me Heal Me" focuses on the disorder of multiple personality disorder and a person who has seven personalities. To cure this, the person gets a secret main doctor who he ends up falling in love with.