When Tom is standing outside looking in through the window this is what he is thinking and seeing:
But in the security and relief of his new position, he simply smiled; with only a sheet of glass between him and the room just before him, it was not possible that there wasn't a way past it. Eyes narrowing, he thought for a few moments about what to do. Then his eyes widened, for nothing occurred to him. But still he felt calm: the trembling, he realized, had stopped. At the back of his mind there still lay the thought that once he was again in his home, he could give release to his feelings. He actually would lie on the floor, rolling, clenching tufts of the rug in his hands. He would literally run across the room, free to move as he liked, jumping on the floor, testing and reveling in its absolute security, letting the relief flood through him, draining the fear from his mind and body. His yearning for this was astonishingly intense, and somehow he understood that he had better keep this feeling at bay.
He took a half dollar from his pocket and struck it against the pane, but without any hope that the glass would break and with very little disappointment when it did not. After a few moments of thought he drew his leg onto the ledge and picked loose the knot of his shoelace. He slipped off the shoe and, holding it across the instep, drew back his arm as far as he dared and struck the leather heel against the glass. The pane rattled, but he knew he'd been a long way from breaking it. His foot was cold and he slipped the shoe back on. He shouted again, experimentally, and then once more, but there was no answer.
The realization suddenly struck him that he might have to wait here till Clare came home, and for a moment the thought was funny. He could see Clare opening the front door, withdrawing her key from the lock, closing the door behind her, and then glancing up to see him crouched on the other side of the window. He could see her rush across the room, face astounded and frightened, and hear himself shouting instructions: "Never mind how I got here! Just open the wind--" She couldn't open it, he remembered, she'd never been able to; she'd always had to call him. She'd have to get the building superintendent or a neighbor, and he pictured himself smiling, and answering their questions as he climbed in. "I just wanted to get a breath of fresh air, so--
He couldn't possibly wait here till Clare came home. It was the second feature she'd wanted to see, and she'd left in time to see the first. She'd be another three hours or--He glanced at his watch: Clare had been gone eight minutes. It wasn't possible, but only eight minutes ago he had kissed his wife good-by. She wasn't even at the theater yet!
Tom realizes several things: how near his livingroom is but he can't get in; how just a short while ago he was kissing his wife goodbye; he realizes the absurdity of his position outside the window; he realizes he has to keep his emotions under control in any way he can.
His revelation is that he can control his mind and keep trying.