A woman has been missing for a month. Police say the person who could help, won't.

Karen Ristevski is 47 years old.

One day, after she had an argument with her husband about financial matters, she went for a walk to clear her head.

That was a month ago. She hasn’t been seen since.

Now, the person who might hold the key to her disappearance has put up a “wall of silence”, the Herald Sun reports.

Police are stepping up their efforts to find Karen, from Melbourne, after a crucial person of interest suddenly stopped giving them information.

An information caravan has been set up in Karen’s home suburb of Avondale Heights today. Officers are planning to go door-to-door questioning local residents.

The neighbourhood is lined with posters bearing her photo and flyers will be appear in letter boxes and local businesses over the next 24 hours.

The 47-year-old disappeared on June 29. She was last seen by her husband, Borce Ristevski, who has been questioned by police and released without charge.

He reportedly told police the couple had been fighting over financial issues and she’d gone for a walk to “clear her head”, which was not considered unusual for the mother-of-one.

What is more unusual is that Karen has made no withdrawals from her bank account since, although she may have been carrying around up to $850 cash at the the time, reports say.

Her mobile is switched off, rendering it untraceable.

Detectives are hoping to speak to a female dog walker who claimed to have been accosted by a strange man on the footpath behind the Ristevski house.

Last week, another man claiming to be Karen’s stepson came forward after being interviewed at Sunshine police station on an unrelated matter.

Anthony Rickard, 32, who admits to struggling with ice addiction, told missing persons detectives he did not kill his stepmother but was “capable”.

He also claimed to have spoken to her on the phone just ten days before her disappearance.

“I said [to police], ‘If you’re going to say it, say it’,” He told the Herald Sun

“So I got them to say, ‘Did you kill your stepmum?’.

“I said, ‘I would have liked to … ‘.”

Rickard revealed he and Karen had previously discussed her plans to leave his father, whom he did not think “had it in him” to kill her.

“It was a shock that she disappeared after my phone call to her.

“I had nothing to do with that besides calling her to confront her — the next thing I know she’s gone.

“Then I felt the guilt that it was because of me, ringing up to confront her,” he said, adding that his first thought was that she may have taken her own life.

He had been calling to discuss an ongoing family conflict being “swept under the carpet”.

Police are urging anoyone who sees Karen to call triple zero (000) and anyone with information to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report to www.crimestoppersvic.com.au