Cynthia Sumpter was last seen playing in the front lawn of her family's apartment on Elm Street in San Jose, California on April 27, 1974. Despite an extensive search of the area, Cynthia has never been found, and her disappearance remains unsolved to this day.

Shortly before her disappearance, Cynthia was allegedly sexually molested near her home. Her mother pressed charges against the man identified as her abuser. Several days after Cynthia vanished, a man claiming to have taken her demanded a $1,000 ransom from her mother in exchange for her safe return. However, this turned out to be a hoax, and the man was charged with attempted extortion.

Cynthia's parents had a bitter divorce a year prior to her disappearance, and both accused each other of hiding her. However, both parents passed polygraph tests, and police ruled them out as suspects.

Two possible suspects have emerged in the case. Antonio Madrid, the stepfather of one of Cynthia's friends who lived just 100 yards from her apartment, was investigated for possible involvement. After Cynthia disappeared, Madrid died by suicide, and police found a bloodstained shirt belonging to him, as well as blonde hairs in his car.

Eugene Joseph Wesley, a convicted murderer, also took two polygraph tests about Cynthia's case, which indicated he knew more about her disappearance than he was admitting. However, he was never charged in connection with her case and has since died in prison.

Cynthia's mother has since moved to Pocatello, Idaho, and believes that her daughter may still be alive. Police suspect that Cynthia was abducted by a non-relative and foul play is suspected in her case.