“What’s the matter with this place?” grumbled my grandfather. “The water’s supposed to be on. Why isn’t the water on?”

“Don’t worry, Grandpa. I don’t mind.”

“Well, I mind.”

We made our way back to the grassy stretch where we could let Barney off the leash. Strictly speaking, this was against the rules. When Grandpa knelt to unbuckle the leash, I felt honor-bound to say: “Isn’t this against the law?”

“It’s a weekday,” he scoffed, still annoyed about the empty fountain. “There’s no one around. Where’s the harm in it? You have to keep your own counsel.” That was one of his mottoes.

I threw Barney his tennis balls before we settled onto one of the weather-beaten side benches. He galloped off, doing his best to track the bouncing balls with jerks of his head. He preferred to catch them midair rather than to nose them out of the grass, but these days his jaws mostly snapped the air. He never seemed to mind. There was bound to be something foul and delicious to check out on the way.

“Have you ever read the Cat and Dog Diaries?” I asked.

“What are they?”

“This thing someone put online. The cat one goes: ‘Another day in captivity. My guards give me hash and some kind of dry crackers, while they dine like kings on fresh meat . . .’ The dog one goes: ‘Waking up. My favorite thing! Food in my dish. My favorite thing! A ride in the car. My favorite thing!’ Get it?”

“I think so.” He smiled.

“Chasing balls with arthritis in my hips. My favorite thing!”

Barney came toward us with his lopsided gait, the balls tucked in the loose skin at the sides of his mouth where retrievers hold their birds. He made a detour to offer his services to a Frisbee game before dropping the balls one by one at our feet, grinning like a lunatic. Twelve years old and still a lot of life in him.

My grandfather scrubbed Barney’s ruff with both hands. “Tell me about it,” he crooned into the watery eyes. “Tell me all about it.”

I picked up a ball and flung it, making a face. “Slimy disgusting tennis ball! My favorite thing!” Barney hurled himself away. It never crossed his mind that he was old. “And he tries to trip his owner,” I said.

“Who does?”

“The cat writing the diary. ‘Next time I’ll try it at the top of the stairs.’ ”

“That’s a bit extreme, isn’t it?” asked Grandpa mildly. “Would your cat do that to you?”

“Of course not! Cloud luuuves me.”

“Well, then.”

“But she’s still a kitten.”

“Wait ’til she gets to be a teenager. Then watch out.” My grandfather laughed with his narrow teeth and laid his hand on my head. I liked the weight of it through my baseball cap.

“Grandpa?”

“Yes?”