When six-year-old Jack Thomson's mum was diagnosed with breast cancer in 2010, he was able to get through the hard times with the help of a four-legged-friend.
Now his family is appealing for any sightings of Jack's dog Toby, who has been missing for nearly a week in the Puketapu, Poraiti area.
"It's breaking my son's heart, he's devastated," Jack's mother Tania said.
When she was diagnosed with breast cancer six years ago, the first thing she did was get Jack a dog "so he could have a friend while I went through treatment".
They adopted Toby - a bull terrier crossed with a whippet, or sheep dog - from Viks Rescue.
As Ms Thomson underwent chemotherapy and began losing her hair, she said Jack "watched his young, vibrant, fit, healthy mother just change overnight".
"Every time things got hard, Jack would go out and sit on the front step and just put his arms around Toby," she said. "Getting him for Jack was the best thing I ever did."
Recently celebrating five years in remission, Ms Thomson said she was one of the lucky ones. Without Toby, she said "Jack's journey coping with my breast cancer would've been unbearable".
Jack, now 12-years-old, had also helped Toby - who had been mistreated by his previous owners.
Watching him grow from a timid dog who did not trust anyone, to a dog who was able to calm other mistreated dogs was very special, Ms Thomson said.
The family has been left "devastated" after Toby went missing on Monday, when he and Ms Thomson's dog Pete wandered away from their Puketitri Rd home.
Although Pete was found at a house on Rotowhenua Rd, in Poraiti, Toby is still missing.
"I am terribly upset, I miss him so much," Jack said. "He's my best mate."
The family have driven around the Puketapu area looking for the dog, visited the pound and the SPCA, and distributed flyers - without luck.
As the area the two dogs walked through was remote farmland, Ms Thomson said she was appealing for anyone who had seen the dog to get in touch.
"I fought for my life with Toby's help so now I'm going to fight for his".
-There are 47 collection sites across Hawke's Bay today for the last day of the New Zealand Breast Cancer Foundation Pink Ribbon Appeal.