My parents began to swap body parts after we'd all moved out. Elijah, the youngest and last to leave, was also the first to notice. He'd dropped by to pick up something he'd left in the move and found our father, in the den as usual, wearing mother's left arm. Met with Elijah's wide eyes, the man had only shrugged, saying, We thought we'd give it a try.

Jonah, the oldest, thought it was distasteful, and didn't hesitate to express his opinion by refusing to join us for Thanksgiving -- our first since they'd been living alone. Elijah, whose loyalty wasn't challenged so much as his stomach, was present for the meal, but couldn't eat much. For my part, I was glad they were still experimenting. It took a while to get used to mother's limp while wearing a man's longer leg, or my father holding his drink in the dainty way his wife's hand knew how, but I didn't feel it was my place to judge.

It even became rather endearing. So long as we'd all lived together, I'd never seen the two so cuddly, so cute, so quick to utter small but meaningful mouthfuls about one another, and often they'd simply stop, and smile, and pat their borrowed body part. Even Jonah had to admit, though only reluctantly, that they seemed happier. Elijah, overcome with enthusiasm, once even asked them to trade in front of us, to show us. But one look at mother's downcast eyes was enough to prevent the repeat of such a trespass. Some boarders, it seemed, were still intact.

Their doctor was firmly against the practice. We didn't find out until later -- he broke confidentiality to let slip his warning -- but our mother's immune system was suffering from the constant shuffle, the mixed blood, the awkward muscle movement necessary to compensate for the imbalance. She'd come down with pneumonia. Father's body, built with a hammer and nails, faired better, but his colds lasted longer, his breath was short, and his eyesight was failing fast.

"Make them stop or they'll do one another in," the doctor told us. We had to remind ourselves he'd called out of concern.

But they wouldn't listen. My brothers had their own tactics: Jonah's to stomp around and raise his voice, Elijah's, most often, simply to cry. I didn't see it so clearly myself. What's good for a person? I tried to explain how they might trade other things, like letters, or backrubs. I taught them Go Fish. But my heart wasn't in it. And after they'd made clear their intentions to continue, I accepted the fact not without a measure of relief.

Having overcome this social obstacle, they began to expand. No longer sticking with the easy pieces, they began trading fingers and toes and ears and lips and all these small details made interacting with them quite disorienting. Seeing my mother enjoy the larger opening afforded by my father's mouth, sucking down enormous portions of gravied-up turkey or huge sections of Christmas ham, was a bit disturbing, even, and I sympathized with poor Elijah, who had to excuse himself on a number of occasions.

And in time the confusion grew, as there were some other, unanticipated, consequences of our parents' behavior. Along with their quickly failing health came certain emotional difficulties brought on by their physical evolution, that we, their children, had to face. I mean that it became hard to tell them apart.

To speak with them then, towards the end, was a rapid rotation of the cool, proud feelings we associated with our father and the warmer, almost sexual but unmistakably blind emotions we had for our mother. We watched for subtle signs of who they might be more of at any given time, and spoke to it quickly, before we were again unsure.

By this time Jonah had had enough. He'd ask Elijah or I how they were, but only nodded gravely at our answer, sensing our uncertainty, as if he already knew and was just making conversation. Elijah eventually moved back in -- there were health issues he'd attend to -- though he kept to himself most of the time, performing his duties with the deliberate resignation of a nurse working triage. I stopped by regularly until the very end. After I'd worked past the confusion, the disorder, I began to actually enjoy not knowing, allowing them to inhabit one another, symbiotic, to haunt one another like ghosts.

When the first one died there was argument over who it was. Jonah, detached and sticking to the facts, said it had to be mother, whose early demise was predicted by their physician. But Elijah kept looking into the remaining parent's eyes, which spent most of their time staring vacantly at the stubborn objects they'd been left with, and swearing he saw her in there. I felt bad that I couldn't tell, but I couldn't bring myself to make much of an effort. After all, maybe they didn't want us to know; maybe they'd been preparing for this the whole time. Besides, I thought, watching the bent shape, so still now without the once interminable shuffle, soon it won't matter at all.