60 Minutes: How police uncovered one of Australia's most sadistic killers

When the body of a two-year-old girl was found in a suitcase dumped on the side of a remote South Australian highway in July 2015, a shocked nation mourned the unidentified child.

But there were questions too.

Who was the child? Where were her parents? And why hadn’t anyone reported her missing?

As the search began for answers, the last thing anyone expected was those bones would hold the key to solving another murder that had happened five years earlier, over 1000 kilometres away.

This Sunday on 60 Minutes, Sarah Abo reports on the horrific murders of mother and daughter Karlie Pearce-Stevenson and Khandalyce Pearce.

Abo reveals the extraordinary police investigation across two states that led detectives to uncover one of the Australia’s most sadistic killers.

It was 2008 when Karlie and Khandalyce abruptly left their home in Alice Springs with Karlie’s boyfriend Daniel Holdom.

Her family caught by complete surprise when they left the Northern Territory so suddenly, without goodbyes or fanfare.

“The whole decision to leave town was a bit of a shock,” Karlie’s Aunt, Sharon, tells 60 Minutes.

But nothing could prepare family and friends for the shock that would follow.

It is now known that a few weeks later, Holdom took Karlie to the Belanglo State Forest – the notorious killing field of backpacker murderer Ivan Milat – where he sexually assaulted and killed her.

Four days after that, Holdom murdered two-year-old Khandalyce.

However, it wasn’t until 2010 that Karlie’s badly decomposed remains were found.

For five years police and forensic pathologists worked to identify her, without success.

Then, in an extraordinary coincidence, on July 2015, a motorist driving along the Karoonda highway near the tiny town of Wynarka, South Australia, found an abandoned suitcase.

Inside, he found a child’s skeleton – Khandalyce.

The grisly discovery was the tragic breakthrough in the case.

A massive police investigation was then able to connect the two crime scenes and ultimately catch Holdom, the monster responsible for the murders.

Former detective Clive Small, who caught notorious serial killer Ivan Milat in the Belanglo forest, says there are haunting similarities between the backpacker murders and the killing of Karlie and Khandalyce.

“I’ve seen some pretty notorious murders over my time but really this takes the cake,” Small tells 60 Minutes.

How did police finally catch the killer, and how did Daniel Holdom manage to keep up the façade that Karlie and Khandalyce were alive for so many years?

‘Evil in the Outback’ airs on 60 Minutes this Sunday at 8:30pm on Channel 9. For more information on 60 Minutes, visit the official website.