What are at least three ways in which Finney creates intense, hold-your-breath suspense, and at what moment is the suspense the greatest...

Jack Finney creates intense suspense through descriptions of what it is like on the ledge of the eleventh floor and what lies below the ledge, the fear and terror in Tom, and the crisis of the apartment window closing.

• What it is like on the ledge and what lies below

Once Tom Benecke makes up his mind to go after the yellow sheet containing weeks of gathered data, he climbs out of his apartment window onto the eleventh floor apartment. Inching along this ledge as he inserts his fingers between the bricks, Tom reaches the yellow sheet, which is at a corner of the building. First, he carefully places his feet on the ledges of each wall. Then, by bending his knees and sliding his body downward, Tom bumps his forehead along the "brick V" until he can retrieve the yellow paper.

At the same instant he saw between his legs and far below, Lexington Avenue stretched out for miles ahead.

He saw in that instant, the Loews theater blocks ahead past Fiftieth Street, the miles of traffic signals, all green now; the lights of cars and street lamps, countless neon signs; and the moving black dots of people. And a violent instantaneous explosion of absolute terror roared through him.

• The fear and terror in Tom

To keep himself from fainting, Tom must draw deep breaths and concentrate upon holding his consciousness. In his terrible fear, Tom shouts "Help!" but the wind and the blank wall muffle his cries. No one will hear him, Tom realizes, "...he had to try moving; there was nothing else he could do." He concentrates his mind upon placing one foot, then another, then the other foot, then the hand as he trembles and has but one thought at a time.

But he could feel the terrible strength of the pent-up horror on just the other side of the flimsy barrier he had erected in his mind; and he knew that if it broke through he would lose this thin artificial control of his body.

During one slow step he tried keeping his eyes closed; it made him feel safer....Then a sudden rush of giddiness swept over him and he had to open his eyes wide, staring sideways at the brick. 

• The crisis of the window snapping shut

Tom has to be careful not to look out and see the windows of the buildings across the street and the void between. Nevertheless, the remoteness of safety causes Tom to stumble. As his right hand smacks against the window and under the weight of Tom's "...sagging body, the open window dropped shudderingly in its frame till it closed and his wrists struck the sill and were jarred off."

For a moment he kneels with his knee pressed against the edge of the ledge. His body sways, fighting for balance.

For an instant he hung suspended between balance and falling...then, with a focused concentration of all his senses, he increased even further the strain on his fingertips hooked to these slim edgings of wood....He couldn't open the window....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.

Perhaps, the moment in which the plot is most suspenseful is that when Tom has his last chance at breaking the closed window of his apartment. Tom calculates how to strike the window; then, he decides that he must punch the window from the shoulder,... he knows that he has but one chance to live.