This summer, I took Indigo for one last walk. She was slow and unsteady on her paws. She looked up at me mournfully. “You did say you’d take care of me, when the time came,” her eyes said. “You promised.”

She died on an August afternoon, a tennis ball at her side.

Sometimes, this autumn, I’d find myself looking for her, as if she might be sleeping in one of my children’s empty bedrooms. But she wasn’t there.

When you lose a dog, you not only lose the animal that has been your friend, you also lose a connection to the person you have been. For a dozen years, Indigo had been a constant, part of the glue that held us together. Now she was gone.

Then one day I got a call from the place where we board our dogs when we are out of town, a “bed ’n’ biscuit” called Willow Run. One of their customers was dying of cancer. Her dog, Chloe, was a black lab, and she needed a home. We rolled our eyes. They had to be kidding. We were in mourning, and we were pretty sure we didn’t want another big dog, especially an older one, and we were just too banged up. We told them we were sorry, but no.

Then, one weekend when I picked up Ranger after an overnight at Willow Run, I met Chloe. Her face was soft. I asked, maybe I could just take her home for a day? You know how this story ends.

Over three million dogs enter animal shelters in the United States annually. Many of them are strays that are returned to their owners; 1.6 million other dogs are adopted. But more than 600,000 dogs are euthanized every year because they do not have a home. People wanting to adopt a pet can contact one of the many organizations working on animal rescue: the American Society for the Prevention of Cruelty to Animals, AdoptAPet.com, the Humane Society.