More than 450 people are listed as missing in New Zealand every year - and while most are found within hours or days, some have simply vanished.

Their families beg, plead, appeal for information.

"Someone must know something," they usually tell reporters, the details of their story differing but their desperation for answers sadly not unique.

Tracey Donnelly finds herself talking to reporters every few years. She's used to the calls now, used to the questions and running through the answers.

But what she will never get used to is not having her husband Jim by her side, and not knowing - or even being close to knowing - what happened to him.

Jim Donnelly was a scientist working at the Glenbrook steel mill, southwest of Auckland.

On June 21, 2004, Jim left the home he shared with Tracey and their children Liam and Siobhan and went to work.

He parked his car, walked into the mill, went into his office and then - nothing.

Jim hasn't been seen since.

At least, not by his family or anyone outside the mill.

His wife spoke about his disappearance for Herald podcast A Moment In Crime. She firmly believes there are people who not only know what happened to Jim that day - but are responsible for it too.

"We were a normal, everyday family - two parents working to pay the mortgage and childcare," she said.

"We had two children we were raising, they were going to school and we were just going about our lives in a normal way.

"I don't know what it was that destroyed that.

"My opinion is that it does revolve around the mill, something was happening inside the mill and I think he saw something he shouldn't have - and it's gone from there.

"If you had told me at the beginning I would think that, I would have told myself that I was incredibly silly, that this could not possibly happen to Jim.

"But as time has gone on, we have got no answer and it's more and more clear that he has been removed by other people rather than himself.

"Because if he had committed suicide, there would have been a body - so, my thing is my husband went to work, he was last seen at work and he's never come home."

In the weeks before Jim disappeared things were strained at home.

Something was troubling the 43-year-old but he wouldn't - or possibly couldn't - tell his wife what it was.

He was stressed, anxious and not himself at all.

"He was very preoccupied with something," Tracey recalled.

"There wasn't a normal atmosphere in our home … there was something on his mind. And I really don't know what it was.

"From what I can see now, he thought he was handling it and sorting it out. But I think that it was bigger than he imagined."

The weekend before Jim vanished was strange, to say the least.

He told Tracey he had to go to a meeting, went and hired a suit to wear and explained he might be "a little fragile" when he came back. But he wouldn't disclose any more.

"That really concerned me a lot," said Tracey.

"I came back to him about five or 10 minutes later, after thinking about that, and said to him, do you mean fragile physically or mentally?

"He said physically and I thought, what have you got yourself into?, and I really didn't know what to do."

Jim went to the meeting and when he returned less than two hours later he was fine. Not a scratch.

Tracey was relieved but still worried and in the dark about her husband's stressors.

Over the next day he paced, he was preoccupied.

He took his son to the driving range to hit some golf balls and when he came back he was very agitated, telling Tracey he had to "go and avert a crisis".

"I didn't know what to think ... the whole weekend was a bit surreal," she said.

"He eventually came home that night and he still wasn't relaxed … I didn't get much further with him, I just thought, he obviously has a lot going on and he's not about to tell me, so there's not a lot I can do at this stage."

On Monday Jim got up for work as normal. He woke his wife, they chatted and he headed off.

When Tracey got to work she confided in her boss about the "weird" weekend and her frustration and worry.

She also spoke to Jim's best friend Stephen - who he'd known since age 5 - and his wife.

They planned to get the men together that night for a talk, to see if Jim would open up to his mate.

Stephen called Tracey back soon after - he'd just heard that a man had been trespassed from his workplace the day before by security.

The number plate matched Jim's car.

"That's when Stephen said, 'I don't like the sound of this, this is sounding very odd'," Tracey explained.

"He went down to the steel mill, to see if he could get hold of Jim. Then he rang me back and said, 'they're saying he's not at work'."

Stephen and his wife raced to the Donnelly home to see if Jim was there.

Nothing.

Tracey's world started to spin, she left work and went to her parents' house.

Steven returned to the mill and asked the staff to look for Jim again.

"Eventually they located his car in the car park but it wasn't in the normal space, he'd parked it somewhere else.

"That's why they'd initially thought he'd left and wasn't on site.

"At that stage, they started looking for him … and then they asked me to go down to the police station and report him missing, just to set things in motion."

Talking about Jim is hard for Tracey, even after all this time.

He was a private man and she dreads to think how he would react knowing their personal story is now so public.

But she will never sit back, never rest until there is an answer.

"We have to do this to try and find out what happened," she said.

"Where the hell is my husband? He went to work and where is he? What's happened to him?"

After the alarm was raised with police an extensive search kicked off.

The investigation found that Jim stopped for petrol on his way to work and bought a muffin with his fuel.

At work, he parked, signed in and went to his office, placing the muffin on his desk.

He changed into his work uniform.

And that's when the trail stops.

He was due at a shift handover meeting but never showed up.

His computer was not switched on.

"My initial thoughts were that he'd fallen over or had a breakdown, that it was just a matter of time till they found him," Tracey said.

"That was very logical, that we would just find him somewhere and he wouldn't be conscious."

The search covered the mill, its grounds, the surroundings - paddocks, beaches, waterways and bush.

Nothing.

Jim's colleagues were spoken to.

Sightings near and far from the mill were followed up.

Footprints on a beach, a man bolting across the motorway.

Nothing.

His mates went out at night to recheck areas already searched, thinking maybe he would come out for them, maybe he was afraid of the authorities for some reason.

They left food in case he was watching from somewhere, hungry.

Still nothing.

"It was like walking through mud," said Tracey.

"I was just barely functioning … it's indescribable - unless you've gone through it - it's just this void that you're living in.

"It was just this waiting - waiting to find out what had happened, waiting for some news, just constant waiting."

Five days later Jim's hard hat was found beside an acid vat inside the mill.

After draining the acid bath, they found his work ID card, PalmPilot, safety glasses, credit card, cash and a single key - his work key.

The keyring with all his other keys was never found.

"I remember my stomach nearly falling out to my knees," said Tracey of the moment she heard Jim's hard hat had been found.

"That was a horrible 24 hours while they drained the acid bath."

There were no human remains in the bath and soon after the search had to come to an end - clues were like hen's teeth.

Mill management were convinced Jim had left the site.

But Tracey wasn't and still isn't convinced.

One thing that has always bothered her is an unidentified car that pulled into the mill car park the night Jim disappeared.

It pulled up near where Jim's car was parked, far from his usual space.

Police were already on the scene by that stage and when the driver spotted the uniforms, the patrol cars, they turned off their lights and drove away.

"The car was never identified, it was never seen again,' said Tracey.

"So my thoughts were that because Jim's car key had never been found, that someone was going to move the car and make it look like he'd left the site.

"But because we raised the alarm earlier than expected, that was unable to be done."

It's been 17 years since Jim was last seen and his family have had to learn how to navigate life without him.

"It's been really hard from that day the search was called off," said Tracey.

"What do you do as a family? You can't just turn around and carry on.

"I had to let the children know that Dad was missing and I had no idea where he was, or how he was, whether he was alive or dead.

"I was just trying to make sense of it. I couldn't work, I was off on sick leave, I actually couldn't deal with life at that stage, it was hard enough just getting out of bed and putting one foot in front of the other.

"The trauma that a person goes through with something like this … it pretty much pulls you apart and it's very hard to put yourself back together.

"I was really not in a good space … I didn't know whether I was grieving for someone that had died, waiting for someone to come back, or waiting for a body to be recovered, if he committed suicide.

"I didn't know what I was waiting for. I was just waiting for a phone to ring all the time. And when the phone did ring, I'd jump and wonder what it would be about.

"It's been horrendously hard, mentally, over the last 17 years … It took 10 years, until I actually started to feel some form of normality.

"It's the not knowing why we've had to go through all of this, - why did this happen?"

Jim's case has never been closed and will remain open until there are answers.

Over the years police have followed up numerous tips, to no end.

They've been back to the mill, spoken to people, taken specialist sniffer dogs all over the site.

Still nothing, still no Jim Donnelly.

"The only place that they have never been able to search is the oxidation pond - because it's rather large and full of not-nice stuff," said Tracey.

"I think whatever happened to Jim happened that morning. I don't think he was alive after that morning - that is my belief."

Over the years Tracey has done countless interviews and in recent years she's thought 'this will be the last one' each time she agrees to sit down with a journalist.

But then she changes heart - she wants Jim's story told, she wants to keep the case alive until that crucial clue emerges and she can bring her husband home.

"I'm not interested in prosecuting this anymore, I just want to know what happened to my husband," she said.

"I miss him so much, I miss him for me and for the children - they have missed out on so much not having him around. He would have been the most amazing father to them… that's the thing that upsets me the most is that he was the most incredible Dad.

"I miss having him here, talking to him … I wanted to grow old with him … not having that person and not understanding why I don't have that person is the hardest part.

"This has been an incredibly long journey and obviously, it's not over yet.

"This last 17 years has been really hard - I would not wish it on anybody.

"While I've moved on, and I am in another relationship, I still can't forget ... I still think about him a lot. Most days."

Once again, Tracey is urging anyone with information to come forward.

All she wants is to know where Jim is, how he died.

To her, the rest is irrelevant.

"Jim was very important to me, and he was my husband and I loved him," she said.

"I just want to know what happened, I just want a kind of peace so I can put this to rest and move on.

"In many ways I have moved on, and I've got a really good life now with my children and with my partner and his children, and things are really good.

"But it's just the missing bit - why?

"Initially, back in the beginning, when I was being interviewed by another reporter they said 'you may never know' and I just thought that was ridiculous at the time.

"I never thought I would get to 17 years and not know."

DO YOU KNOW ANYTHING ABOUT JIM DONNELLY'S DISAPPEARANCE?

If you have information please contact Inspector Dave Glossop [email protected]

Or you can contact Herald journalist Anna Leask [email protected]

To pass on information anonymously contact Crimestoppers on 0800 555 111