On his first morning of retirement, Edwin Marsh swept the old Hollowbrook post office one last time. Behind a coat rack he found a brass mail slot in a wall that never had one. The little plate read TOMORROW'S DEPARTURES. As a joke, he scribbled a grocery list and fed it in. By noon, the milk he'd written down sat on his porch, in a glass bottle stamped with tomorrow's date.

Edwin decided the slot was a trick, maybe a prank from the new postmaster. He marched next door to ask his neighbor Rosa if she'd seen anyone sneaking around his porch that morning.

Rosa hadn't seen anyone. But she told Edwin the old post office was set to be torn down next week to build a parking lot. If the slot was real, he was running out of time to use it. They hurried back to take a closer look.