As the lead vet at a last-stop California animal shelter, Dr. Kwane Stewart dealt with waves of intakes and discouragement. It got to him.

That’s not uncommon among people who work with animals: You go in knowing you can’t save them all (though of course you want to). Then human stuff piles up … irresponsible pet ownership, abuse, neglect, bureaucracy, you name it — and you wonder if you can do anything at all.

Stewart began to stop and talk with the area’s homeless people who had pets, offering his services pro bono. Despite the initial mistrust — how did they know he wasn’t going to take their dogs or cats away? — he found renewed purpose. He details this journey in What it Takes to Save a Life: A Veterinarian’s Quest for Healing and Hope.

“Homeless people are loving, dedicated pet owners — which I hadn’t thought the case before I started my work,” he writes.

Another surprise was how well behaved the dogs were. In clinics, he’d seen his share of out-of-hand dogs whose humans insisted they had no time to train them. The dogs of the homeless did not pull at their leashes, bark or growl when Stewart approached, nor did they attack other dogs. These owners had nothing but time. They and their canine companions could read each other perfectly.

Stewart has also been inspired by those who weren’t homeless, but still pretty beaten down by the circumstances of their lives. One of these was Richard, a Vietnam veteran who lived in a trailer with his wife and several rescued animals. When Richard’s dog Courtney, a Corgi-hound mix, required a $3,000 surgery for bladder stones. Richard quickly agreed. Stewart asked if he was sure.

“Do what you’ve got to do. Period. … Courtney’s a member of the family. I ain’t rich now but I’ve been poor and I can and will be poor again if that’s what it takes. … That’s just something that when you become a responsible pet owner, that’s what you’ve got to do.”

Stewart put some info about Richard and Courtney on a GoFundMe page. He was stunned when $17,000 came in within a week. In what he calls one of his favorite details of all time, one of the donors was another pet owner he’d helped.

Another great detail: Stewart also works on TV and movie sets, making sure animal actors are safe and well. He overheard Brad Pitt bragging about how sweet, loyal and intuitive his own dog was. “If I closed my eyes, I could have been on Skid Row, listening to someone on the streets talking about what their dog meant to them.”

There is, of course, much more to this memoir. Stewart’s own history includes being bullied as a child, getting into fights well into adulthood, mental illness, a broken marriage, finding joy in fatherhood and navigating vet med as a Black man.

Stewart now leads the Project Street Vet nonprofit, which currently has teams in California, Florida and Atlanta.