On January 29, 1991, nine-year-old Lee Hyung-ho disappeared from a playground near his home in Seoul, South Korea. Hours later, his family received a call from a man claiming to have kidnapped him. He demanded 70 million won for his return. For more than two weeks, the caller repeatedly contacted the family. He sent Hyung-ho’s father across Seoul with ransom money and seemed to closely watch both the family and police. During one attempted ransom drop, officers mistakenly watched the wrong location, allowing someone to escape with the money. On March 13, Hyung-ho’s body was discovered beneath a highway. Investigators determined he had been suffocated and likely killed on the same day he disappeared. This meant the caller may have been demanding ransom even though Hyung-ho was already dead. Police recorded around 85 minutes of the kidnapper’s voice and received thousands of tips. Investigators examined several suspects, including one of Hyung-ho’s relatives, but no one was ever charged. The statute of limitations expired in 2006. More than 35 years later, the identity of the man behind the chilling phone calls remains unknown. Eerie historical photos: