On Dec. 3, 1957, Kay Ridulph's 7-year-old sister, Maria, was kidnapped by a mysterious stranger known as "Johnny" in Sycamore, Ill.
Kay, who was 15 at the time, wrote about the search for Maria in her diary, offering an in-the-moment account of the investigation:
December 3rd, 1957, Tuesday. When I came home at 7:30 I was informed that Maria was kidnapped. It didn't really hit me until we found her doll by the garage. The whole town formed a searching party which continued throughout the whole night...
Five months later, on April 26, 1958, the case went from a kidnapping to a murder when Maria's tiny body was found partially clothed 90 miles away, near Galena, Ill.:
April 26th, 1958, Saturday. I went to my lesson at 6:45. ... Then Father Duvine came and he told us ... that a body was found. It didn't hit me yet. ... Then I started crying with the boys standing there. She was decomposed down to the skeleton. The cause of death not known yet. But it's very evident our waiting is over.
The wait for Maria's killer to be brought to justice would take much longer.
Kay passed away on Sept, 26, 2011, three months after a shocking arrest in her sister's 54-year-old cold case.
Click the video above to hear "48 Hours" correspondent Erin Moriarty read from the diary.
Moriarty goes inside the investigation of what authorities say is the oldest cold case ever prosecuted in the U.S. in "Cold as Ice."