Raewyn and Edgar Wahnig treasured their son's ashes. Now they have been stolen in a burglary.

"Just bring our boy home" is the plea from devastated Christchurch parents who say their son's ashes were stolen from their Linwood property last week.

The fifth of Edgar and Raewyn Wahnig's six sons, Thomas, was stillborn 22 years ago and his ashes had been kept in a plastic bag tied with red ribbon on Raewyn's duchess since the day the couple took him home.

On Thursday afternoon the house was burgled, and his ashes were taken.

JOHN KIRK-ANDERSON/FAIRFAX NZ Edgar and Raewyn Wahnig painted a sign pleading for the return of their son's stolen ashes.

The ashes meant "everything" to the couple, who were left distraught at the fresh loss of their second youngest child.

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"He completes the unit. He's our son, he's part of us. It just leaves a hole, he's not there", Edgar Wahnig said through tears.

JOHN KIRK-ANDERSON/FAIRFAX NZ Edgar and Raewyn Wahnig had planned to bury their son's ashes together with the first of them to die.

"Bring my boy home and give him back to us," his mother pleaded.

Wahnig said he had been working nearby when he got a phone call to say his security had been activated. He raced home to the alarm still blaring and immediately saw the lid removed from the small box they kept the ashes in.

"I saw the jewellery gone, the wardrobe open, that doesn't matter. The rest of it is part and parcel, it's a break-in but it was the ashes, that was the thing that really hit," he said.

JOHN KIRK-ANDERSON/FAIRFAX NZ The empty box which once held the ashes of Edgar and Raewyn Wahnig son.

"We had one son who had leukemia and we managed to get through that, and the rest have just been little ratbags.

"But we never got to know whether he we going to be as mischievous as the others, just a little soul."

The couple said they never wanted him to feel alone so he had stayed with them in the family home.

"We didn't want to put him in the cemetery by himself so we decided that we would keep him until the first one of us went, and they would take him with them," his mother said.

She had a message for the burglar: "It means nothing to you and everything to us, let someone know where he is."

She suspected the burglars thought her son's ashes were drugs.

Around $20,000 of jewellery was also stolen including a necklace the pair designed together for their wedding anniversary, a ring, and irreplaceable gifts from her late mother. Their passports had also been stolen.

A hammer had been left on the bed from the smashed window and police had fingerprinted the property so the pair hoped it would be only a matter of time until their son was found.

"We can't just do nothing," she said.

Out of desperation, they had spraypainted a sign reading 'Return our son's ashes' that sat on a truck outside their Buckleys Rd property.

Edgar's father had died late last month so it had been an "awful" year for the family.

"If things come in threes, I'd hate to see what the third one's going to be," he said.