Samantha's mum didn't answer when she called on Mother's Day. Then police found two bodies.

For nine-year-old Samantha Kay, Mother's Day 2000 began like any other special occasion, with an excited phone call to her mum Susan.

The call was meant to be filled with "I love yous" and childish chatter, a moment of connection as she wished her mum the happiest of days.

But that day, the phone just rang out. Susan, who always answered her daughter's calls, wasn't there to pick up.

What Samantha couldn't have known was that this silence marked the beginning of an unimaginable nightmare.

Her mother had been brutally murdered alongside her friend Joanne Teterin in Joanne's Newcastle home. Their bodies wouldn't be discovered until three days later, on May 17.

For Samantha and her family, time fractured into 'before and after'. For 25 years, they've lived with a harrowing absence, both of Susan herself and of justice.

They've been forced to navigate birthdays, Christmases and life milestones without her, while Susan's killer has walked free, quietly carrying a secret that denied her loved one's closure for decades.

Now, on the 25th anniversary of the women's deaths, NSW Police have launched a fresh appeal in the hopes new lines of inquiry might finally bring answers for the two families.

Susan Kay was 32 when she was murdered. Police are calling for anyone with information to come forward. Image: NSW Police.

Police said Susan and Joanne were last known to be alive on May 11, 2000.

It's believed Joanne received a phone call, and moments later, answered a knock on the door. The women's killer, likely someone known to Joanne, brutally bashed them inside the Carrington home.

Days later, police forced their way inside the home and made the tragic discovery of the women's bodies.

With the 25th anniversary of the women's deaths approaching, police have set up a team of detectives to re-examine the cold case. They believe new forensic developments could be key to catching the killer.

'My world shattered immediately'.

It's been 25 long years without answers for Susan and Joanne's families.

No one knows this more than Samantha.

In an emotional letter shared with the Daily Telegraph, Samantha spoke of how her father was faced with the unimaginable task of telling his nine-year-old daughter she would never see her mother again.

"My world shattered immediately. I could not believe or accept that my mum was gone. I woke up the next morning, convinced it was just a bad dream," she wrote.

"When I realised it was not, I broke all over again. This occurred on a daily basis for as long as I can remember."

It's a feeling she'll never forget.

Samantha spoke directly to her mother's killer as she called for justice.

Joanne, 37, was also murdered in the Newcastle home. Image: NSW Police.

"I wonder if you still have your mother," she wrote, per The Telegraph.

"I wonder if you have a partner and children now, and if you could imagine having to do what my dad did, that no parent should ever have to do —- and tell their kids their mum is dead at the hands of a truly horrible individual."

She believes there is someone, somewhere who knows more than they're letting on.

And police agree. They're calling for anyone with information to come forward and help bring these families closure.

Homicide Squad Commander Detective Superintendent Joe Doueihi said police are combing through the original investigation and pursuing new lines of inquiry to get justice.

"It was a brutal crime which has remained unsolved for 25 years," he said.

"Homicide detectives are committed to seeking justice for the families of Susan and Joanne.

"We remain focused on finding the person or persons responsible and renew our appeal for anyone who may have held on to information — no matter how seemingly insignificant — to reach out to police.

"The families of Susan and Joanne deserve much-needed answers and justice."

Feature image: NSW Police.