Someone turned off the fridge.
I'm not sure who, nor entirely sure when. It must have been early this morning, or maybe even yesterday evening. It wasn't discovered until this evening, when everything in the freezer was at least partially thawed, and everything in the fridge was barely cool at all.
Luckily, most of what was in the fridge was too-old leftovers and condiments. However, we'd recently stocked the freezer up with meat and veggies. So now we have to use a whole lot of meat in just a few days. Sigh. : (