Nadia named her sourdough starter Gerald, the way you name anything you have to feed twice a day and slightly resent. This morning, taped to his jar in flour-dusted handwriting she did not recognize, was a note: WE NEED TO TALK ABOUT THE THERMOSTAT. Gerald had no hands. Gerald had no pen. And yet there it was, the tape still slightly warm.

Nadia decided the bravest thing was to answer. She grabbed a pen, wrote "WHAT ABOUT THE THERMOSTAT?" on a sticky note, and pressed it to the jar. Then she stood back and waited, arms crossed, feeling ridiculous. A bubble rose to the top of Gerald and popped, like a tiny throat clearing.

By lunch a new note had appeared, written in flour right on the jar: 72 IS TOO COLD. I AM A LIVING THING. Nadia bumped the thermostat up two degrees. Almost instantly Gerald frothed up happily, doubling in size, practically purring. "Okay," she breathed. "Okay. We can negotiate."

Two degrees warmer, Gerald baked himself into the best loaf Nadia had ever made, hopping into the warm oven and out again all on his own as fresh bread. A note rose in the crust: A GIFT. FRIENDS NOW? Nadia tore off a piece and ate it. It was incredible. "Friends," she agreed, mouth full.