When Tom finally makes it back to the window ledge, both he and the reader feel as though the danger has passed. But his wife won't be home for many hours, the window won't open, it's cold, and it's hard for him to keep his balance on the ledge. How will he get in?
First, he tries to smash the window with a large coin, then with his shoe. This doesn't work.
Next, he tries shouting for help again. There's no answer.
Third, he considers waiting for his wife to come home, so that she could get the superintendent of the building to open the window from the inside. But the wait would be too long for him to continue keeping his balance on the ledge. He's really cramped, and he has to move around to relieve the pain in his muscles--and every time he moves, he risks falling to his death.
Fourth, he wonders if someone in the building across the street or in his own building might notice him and come help him. Or perhaps someone on the street below. But even though he can see some people, they can't see him. He tries attracting their attention by lighting some papers on fire with his matches, then waving the makeshift torches around; this doesn't work. He tries getting the pedestrians' attention by dropping coins on them. This also fails.
Finally, Tom makes up his mind to punch his hand through the window. This takes some preparation and some courage, and it hurts, but it works! Tom tumbles into his apartment as he successfully breaks the window with his fist.