A Nebraska girl went looking for a date to a high school dance. One week later, she was murdered.

March 25, 1969, aged 17 Mary Kay Heese never came home from school in Wahoo, Nebraska. Hours later, his body was found beaten and stabbed to death on the side of the road outside the city.

Investigators attempted to trace Mary Kay’s last known movements. A witness saw Mary Kay get into a car with two men on a street corner near her home. But investigators at the time were unable to determine who was in the car. Weeks turned into months without an arrest. Mary Kay’s murder will remain unsolved for decades.

“48 Hours” correspondent Natalie Morales reports on how the murder was finally brought back into focus in “The Girl from Wahoo,” an all-new “48 Hours” airing Saturday, Feb. 14 at 10/9c on CBS and streaming on Paramount+.

In 2015, a new investigation was launched. Ted Green, a criminal investigator with the Saunders County Prosecutor’s Office, was assigned to the case.

“Every criminal investigation is a puzzle,” Green told “48 Hours.” For Green, part of solving this puzzle was learning more about Mary Kay Heese.

Mary Kay’s younger cousins, Mark Miller and Kathy Tull, remember Mary Kay as a happy person who always took care of them. But they said that happiness was sometimes undermined by the difficulties of adolescence.

Green learned that Mary Kay came from a strict home, under the eyes of watchful parents. The situation was different in high school. “There was a group of girls who would round her up and do her makeup at the start of the day and change her clothes,” Green said.

“She wanted to fit in,” Miller told “48 Hours.”

Part of this desire to fit in was Mary Kay’s wish to attend the local Sadie Hawkins Ball – a popular event at the time when girls asked boys to attend.

Tull told “48 Hours” that shy Mary Kay had trouble finding a date. Tull still has a letter from Mary Kay, written a week before her murder, asking her cousin Jerry to attend the dance with her.

“If we pick you up on Friday the 28th or Saturday the 29th, will you go to the Sadie Hawkins Ball with me?” Mary Kay wrote in the letter. “You can wear sports clothes (not a tuxedo or anything) because it’s not a formal dance […] Don’t bring money to enter because it’s the girls who have to pay for everything, including tickets and food.”

As Green learned more about Mary Kay, he came to a conclusion. “She wouldn’t get in a car with someone she doesn’t know,” he said.

The pieces of the puzzle came together for Green, who focused on two names that kept coming up in the old files: Joseph Ambroz and Wayne Greaser, both interviewed in the days after Mary Kay’s murder.

Joseph Ambroz, 22, lived in Wahoo and worked in a slaughterhouse at the time. He was also on parole after serving time for forgery and escape.

Greaser was friends with Ambroz. “He was just this wannabe kid following Ambroz,” said Saunders County Assistant Prosecutor Richard Register, who worked on the case.

Green and Register told “48 Hours” that Ambroz knew Mary Kay. They both frequented the same café and had mutual friends. Green and Register also believe that Mary Kay thought Ambroz was not a threat, but an opportunity to fit in with the crowd.

Green believes Ambroz and Greaser took Mary Kay to a well-known party spot near town and that at one point Mary Kay tried to run away from the car. Green says he thinks Ambroz chased her and eventually stabbed her to death.

“She just wanted a boy to go to the prom with her. And unfortunately the prom she went to was the death of her,” Register said.

More than five decades after Mary Kay Heese was found dead, 77-year-old Joseph Ambroz was arrested for her murder.

In July 2025, Ambroz entered into a plea agreement and pleaded no contest to conspiracy to commit first-degree murder. He was sentenced to two years in prison. Greaser, who died by suicide in 1977, was named as the other person who conspired to kill Mary Kay.

For Mary Kay’s cousins, the plea deal and sentence were an injustice. Ambroz is said to have stolen Mary Kay’s future.

“She had all these years left to live, and Mary Kay never had a chance to live,” Miller told “48 Hours.”