What changed for my 84-year-old grandmother when we slid a sheet under her bed.

My grandmother is 84. She lives in the granny flat behind my mother's house in Mexico City, with two cats, three ferns, and a folder of family photographs she rotates by season. She is sharper than most people I know, including me.

She is also, since approximately 2019, in a constant low-grade negotiation with her own body. Her hips ache when she stands up. Her knees ache when she sits down. She is awake by 3am most nights and lying still in the dark until light. She says she does not mind the lying still. I think this is one of the lies elderly people tell their granddaughters because they do not want us to worry.

The hand-wringing.

Last year my mother and I had a long conversation about her. We had been to a specialist who explained, in the gentle voice doctors use with the elderly, that there is no specific thing wrong with my grandmother. She has, the specialist said, "the wear and tear of a long, well-used life." He recommended ibuprofen, gentle movement, and "as much sleep as she can get, which I appreciate is not much."

My mother and I had been buying her things for a year by that point. A new pillow. A heated blanket. Magnesium. A weighted blanket. A little machine that plays the sound of rain. A foam mattress topper. Compression socks for her ankles, which are kind of swollen and kind of not. None of it had moved the needle. She thanked us each time. She used each thing politely. She still woke at 3am.

I stopped buying her things, because I had begun to feel that I was not actually buying her anything — I was buying myself the feeling of having tried.

The thing my husband's cousin mentioned.

At a family birthday in February my husband's cousin Daniel — he is a respiratory physiotherapist, the most rational person in our extended family — mentioned, in the way you mention things at a Mexican family party, that he had bought a grounding sheet for his own father six months earlier. His father is 79. Has osteoarthritis in both hips. Lifelong insomniac. Daniel said, very dryly, "He has been sleeping six hours a night for the first time since I was a boy."

I asked him three questions. He answered them. He said it had cost less than a moderately good dinner for two and that it had a 90-night trial. Then he said the thing that made me listen: "I did not believe it either. I bought it because I was running out of things to try and I am tired of feeling guilty."

That is exactly what I had said to my mother eight weeks earlier.

The sheet, and the small lie.

I did not tell my grandmother. This is important. I bought the sheet — a stainless-steel grounding sheet from an Australian company called Premium Grounding — and I went over to her flat one Sunday afternoon when she was watching a Spanish-language soap opera with the volume turned up. While she was distracted by a particularly intense plot development, I went into her bedroom, lifted the fitted sheet off her bed, slid the grounding sheet onto the mattress directly underneath, plugged the thin cord into the earth pin of the wall socket beside her nightstand, and tucked the fitted sheet back over the top.

It is invisible. You cannot see it, you cannot feel it. There is no electricity. There are no batteries. There is no app. It is just a charcoal-grey woven sheet with a cord that connects, through the third pin of any wall outlet, to the ground wire that runs into the actual Earth.

I did not tell her because I knew that if I told her, she would believe nothing because she had already decided, at some point in her seventies, that she had stopped responding to new things. So I let the sheet do the work without her permission.

The first morning.

I called her on the Monday afternoon, five days after I had set the sheet up, in a casual tone, to see how she was. She said, in the tone she uses when she is about to mention something she does not want to make a big deal of, "I slept until five-thirty. I had to look at the clock twice. I thought it had stopped."

She did not connect this to anything. She said she had slept badly the next night. She said she had slept until six the night after that. She said it was probably the weather. She said she had told my mother on the phone that she had slept "almost normally" three nights in a row and my mother had asked her if she was unwell. She laughed.

By the third week, when she had told me four separate times in casual conversation that she was waking up at 5:30 or 6am and getting up to make coffee with my grandfather's old coffee pot, I told her the truth. I sat down on the edge of the bed and I lifted up the corner of the fitted sheet and I showed her the charcoal-grey grounding sheet and the cord running down to the wall socket. She looked at it without saying anything for about ten seconds.

Then she said — in Spanish, the way she does when she is being affectionate — "Pues mira, mija. La trampa que le hiciste a la abuela." The trick you played on the old woman.

And she laughed, and asked me where she could buy one for her sister.

What it gave me back.

I want to be honest about this part. The sheet did not erase my grandmother's hip pain. It has not. She still uses the wall to stand up. She still goes more slowly down the steps to the courtyard than she did three years ago.

But she is sleeping. She is sleeping in a way she has not slept in five years. And the unexpected thing about that is that the rest of her has lifted with the sleep. She is more in the photographs. She is more in the kitchen. She makes jokes that are slightly too sharp. She told me last week, very seriously, that the cat had moved his sleeping spot to the side of the bed where the sheet plugs in and was now spending most of the day there.

I think about my grandmother more in the past three weeks than I had in the previous three years. Not because I am worrying about her. Because there has been more of her to think about.

"The trick you played on the old woman." — my grandmother, day twenty-one.