Stale bread isn’t dry bread. You can seal a loaf in a bag so tightly that it keeps almost every drop of its water, and it will still go hard. What changes is the starch. In the oven its tidy crystals swell with water and come apart; as the loaf cools they slowly fold back into order, holding the water tightly in their structure, where it no longer makes the crumb soft. The process has a temperature range, and a fridge sits right in the middle of it, which is why a loaf kept in the cold goes stale several times faster than one on the counter, while a freezer, below the range, nearly stops it. The good part is that the change runs both ways. Put a stale loaf back in a hot oven for a few minutes and the crystals melt again, and for an hour or so it is close to new. Very few kinds of going-off can be undone. Staleness is one of them, because nothing was lost; it was only put away too neatly.