The empty bed.

Jonathan's mouth worked dryly for a moment, trying to call out for his wife, but then something galvanized in his mind, and he decided that if his son was missing again, he would just have to find him and bring him home again--as many times as it took for Clark to understand that he had one real father, and that that father would not tolerate running away.

The farmer turned around, his jaw working, and surveyed the hallway once more before heading for the stairs, which he descended quickly, skipping over the three steps he'd jimmied to squeak after they'd discovered that Clark could sleepwalk. It occurred to him now that his son's absence could be just another incidence of sleepwalking, in which case Clark could be anywhere in the county, although Jon suspected now that his instincts were still sharp and that Clark had only been gone for a few minutes. Even a thought as innocent as sleepwalking didn't quell the now-familiar fear and hollowness.

Jonathan was scanning the yard though the kitchen window, digging in Martha's bit drawer for a box that even she didn't know he'd stashed there, and mentally thinking of what he'd do if he found his son sleepwalking or if he found him awake and running away out of shame, when he caught movement out of the corner of his eye. He froze for a moment, then slowly turned his head to scour the living room with his gaze. A moment ago everything had been still, but now there was a small fire in the fireplace. Trying to push old horror movies out of his mind, he took a slower look around the room.