Two years after John Zera was murdered, an anonymous tip about a Franklin High substitute teacher with an unusual interest in boys' feet would generate a new prime suspect.

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The day after John Zera's body was found, Daniel Acker was found standing over the crime scene in Whitnall Park. His alibi for the day of John's death was shaky, but police dismissed him. Acker would strike up a correspondence with the Zera family and start his own investigation into the case, pointing the finger at a mental patient at the facility where he worked.

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In 2009, police investigating the 1976 homicide of John Zera catch a break when a swim coach is arrested for child molesting. A search of the man's condo reveals clues about John's case.

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Before John Zera, Hales Corners Detective Howard Hingiss had only handled one murder case. While he narrowed down the suspect list, with the help of the F.B.I. and other departments, he would never discover the identity of the murderer. Twenty-five years after his retirement, and almost 40 years after the crime, the question of who killed John remains unsolved.

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On Feb. 20, 1976, freshman John Zera disappeared from a high school in suburban Milwaukee. In the early days, John's family hoped for his safe return. Later, they prayed whoever was responsible for his disappearance would be brought to justice. Finally, they clung to hope that advances in technology or someone with a guilty conscience would someday offer an explanation of what happened to their Johnny. And why.

In this episode, Milwaukee Journal Sentinel reporter Gina Barton looks at how the case began and what drew her to it.

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