‘Adam-12’ Star Martin Milner’s Secret Anguish

There was a tragic secret “Adam-12” and “Route 66” TV star Martin Milner took to the grave, The National ENQUIRER has learned.

A pal said when he died of heart failure on Sept. 6 at age 83, the actor had never gotten over the death of his daughter Amy, who died of acute myeloid leukemia in 2004!

“Before he passed away, Marty said he was ‘not afraid of dying’ because he was certain he would see his beloved daughter in heaven!” said the pal.

Martin, then 71, launched a nationwide search for a bone-marrow donor for his ill daughter when she was diagnosed in 2003.

“Marty did everything he could to save Amy’s life. They got two good matches, but, sadly, it was not in time. Amy was beyond the point where she could have a bone-marrow transplant, and she passed away,” the source said.