84 & STILL CATCHING KILLERS!

There's one case that continues to haunt retired ex-homicide cop Allen

He began his police career at 16, and even in retirement 84-year-old Allen Arthur hopes to solve cases.

The decorated homicide detective covered more than 71 murders in his 40-year career, but he is plagued by the one he never could solve -the 1992 disappearance of Adelaide schoolgirl Rhianna Barreau. It is Allen's dying wish to find her.

"I don't care whether I'm 95 years old - if I can still talk and it'd help, I'd be happy to," he tells Woman's Day. "I'd do anything to see Rhianna's offender caught and punished."

SHOCK DISAPPEARANCE

The grandfather-of-two was one of the first detectives assigned to the case when Rhianna's mum, Paula Barreau, reported the 12-year-old missing after she seemingly vanished without a trace.

It was October 7, 1992, and Rhianna had been home alone while on school holidays.

She had walked to her local newsagency to buy a card for her penpal, but when her mum returned home from work later that day, the Morphett Vale house was empty, and Rhianna nowhere to be found.

The house was locked, the TV on, and the card she bought was still in its wrapper on the table. There were no signs of forced entry. Detectives were stumped.