The first time their youngest daughter asked where they would go if the roads closed, Claire knew she had heard more than Mark intended.

She was nine. She had a flashlight beside her bed and knew where the extra batteries were.

This was sensible.

She also wanted to know whether she should leave school if the power went out, whether the Creamery would still have food, and whether Grandma would be allowed in their house if there wasn't enough for everyone.

Mark had not told her to worry about Grandma.

He had talked about supplies at dinner.

He had watched a video about a prolonged grid failure while their daughter was in the room.

Once, while explaining the family plan, he said that people might become desperate.

Children are excellent at hearing the sentence adults wish they had phrased differently.

Claire wanted the videos off and the emergency talk kept between them.

Mark wanted their daughter to know what to do.

They had each found a way to say, “I'm protecting her,” and each was beginning to wonder whether the other was.

The generator worked.

That was part of the problem.

When the power went out, Mark rolled it into the driveway, ran an extension cord through the garage, and kept the refrigerator cold.

Their daughter charged her phone.

By morning, the neighbors had come over for coffee.

Mark had spent months telling his wife, Claire, that they needed a backup. For once, an argument in their marriage had been settled by an appliance.

Or so he thought.

Claire thanked him for getting the lights on. Then she asked whether he had paid for the generator with their joint credit card. He had.

It cost nearly three thousand dollars. He had bought it six weeks earlier and kept it at his brother’s house because he knew she would object.

“But we needed it,” he said, gesturing toward the humming machine.

She looked at him. “You knew I would object.”

Both statements were true. The refrigerator stayed cold. But their trust took a hit.

The Roman emperor Vitellius reportedly served a dish containing fish livers, peacock brains, lamprey milt, and flamingo tongues.

Suetonius described the meal as evidence of an appetite without restraint. But it was also an achievement of transportation.

Captains brought the ingredients from across the Roman world.

What looked like one man's extravagance depended on the labor of strangers and the ability to move food over great distances. Suetonius, Life of Vitellius, 13.

We notice the flamingo tongues. We should notice the ships.

In Massachusetts, I can buy blueberries in February and decide against them because the raspberries look better.

I can pick up coffee that will be waiting again tomorrow.

The modern food system has placed a kind of imperial reach inside an ordinary errand.

Its most remarkable accomplishment may be that it rarely feels remarkable.

That reach has improved our lives. Trade can help a country through a poor harvest; it allows people to eat a more varied diet than their own climate permits.

It has also taught us to expect the world to answer promptly when we want something. We barely register the winter blueberry. We register its absence.

Lately, I have been thinking less about what I can buy and more about what I should keep.

How long does canned meat last? How much water is enough? What could a well-tended garden actually provide?

Each question has a practical answer.

Together, they suggest that my confidence in the full supermarket shelf has somewhat changed.