Tom steadfastly refrains from looking down while he is edging his way along the narrow ledge to get to his precious sheet of yellow paper. He is a little anxious but not really frightened until he reaches the paper. Then he realizes that he is in an awkward position. Since the ledge is so narrow, he can't bend his knees enough to lower his body so that he can touch the paper with his outstretched fingers. In bending his knees on such a narrow ledge, he naturally forces his body to move back out into empty space..
He couldn't quite touch it, and his knees now were pressed against the wall; he could bend them no farther. But by ducking his head another inch lower, the top of his head now pressed against the bricks, he lowered his right shoulder and his fingers had the paper by a corner, pulling it loose. At the same instant he saw, between his legs and far below, Lexington Avenue stretched out for miles ahead.
Tom is so unnerved by this sight, as well as by the realization of the extreme danger he has put himself in, that he can no longer control his body.
It was impossible to walk back. He simply could not do it. He couldn't bring himself to make the slightest movement.
He realizes that he needs help. The first attempt he makes to attract attention is by shouting "Help!" as loudly as possible. But he quickly realizes that the wind would make his cries sound "directionless and distant." Besides that, he remembered how often he himself had ignored distress cries in the night in the gigantic, cold, uncaring city of New York.
Now that he has seen the reality of his situation and has understood that he is probably going to die in the most horrible manner by falling to his death, Tom forces himself to sidle back along the ledge to the window of his apartment. But at this point he loses his balance and grabs at the open window sill, bringing it down on his hands and forcing him to let go and nearly fall backwards. Now he is unable to open the window from the outside, because this is an old building and the windows do not slide up and down as easily as they were designed to do when the building was new. The windows were counterbalanced with weights and pulleys inside the walls. But over time the cords attached to the weights deteriorated and broke and were never replaced. Besides that, the window frames had been painted countless times over the years, and the paint made the upper and lower panels stick together.
Tom can't break the glass. He tries setting fires to three letters he finds in his pockets and dropping them to the street below. But he can't attract anyone's attention either down below or inside neighboring apartments.
There were a dozen coins in Tom Benecke's pocket and he dropped them, three or four at a time. But if they struck anyone, or if anyone noticed their falling, no one connected them with their source.
It would be a disappointing ending, as Jack Finney knew, if Tom were rescued by some stranger. (That is called a deus ex machina ending.) In the end Tom has to save himself. He manages to smash the window-glass with his fist.
And then, kneeling there on the ledge, an arm thrust into the room up to the shoulder, he began picking away the protruding slivers and great wedges of glass from the window frame, tossing them in onto the rug. And as he grasped the edges of he empty window frame and climbed into his home, he was grinning in triumph.