Tom Benecke is not a kid but a mature, married man who has a good job and a good future ahead of him because he is obviously smart, ambitious, and courageous. The author, Jack Finney, wanted to write about a man walking on a narrow ledge high above the streets in Manhattan. His biggest problem was to make it plausible that his hero would actually do such a crazy thing. The fact that Tom's wife had gone off to the movies and left him all alone is very important, because it is pretty obvious that she never would have let him climb out the window onto that ledge. Women have better sense than men. Finney devotes five paragraphs to explaining what is going on inside Tom's mind before he makes the decision to climb out on the ledge and retrieve his important memorandum.
The first paragraph begins with this sentence:
It was hard for him to understand that he actually had to abandon it--it was ridiculous--and he began to curse.
In the second paragraph he is still telling himself not to risk his life for a piece of paper:
For many seconds he believed he was going to abandon the yellow sheet, that there was nothing else to do.
Then in the third paragraph describing his indecision:
But just the same, and he couldn't escape the thought, this and other independent projects, some already done and others planned for the future, would gradually mark him out from the score of other young men in his company.
The next paragraph shows he is beginning to consider doing what he knows is foolhardy:
By a kind of instinct, he instantly began making his intention acceptable to himself by laughing at it. The mental picture of himself sliding along the ledge outside was absurd--it was actually comical--and he smiled.
And in the fifth paragraph describing his fears and temptations:
It occurred to him that if this ledge and wall were only a yard above the ground--as he knelt at the window staring out, this thought was the final confirmation of his intention--he could move along the ledge indefinitely.
In other words, it was only the great height that presented a problem. Walking along the ledge would be easy as long as he didn't lose his nerve. And he believes he won't lose his nerve as long as he just doesn't look down. The author devotes five full paragraphs to having his character rationalize doing something that seems nearly suicidal once he is actually out on the ledge.
Thus, once Tom Benecke is out on the ledge, shuffling along a precarious foothold eleven stories above Manhattan, the reader has become persuaded that his behavior is plausible. If the reader didn't believe that Tom's decision and course of action were credible, the reader would refuse to identify with the hero--and identification with the hero is essential to appreciation of the story.
Many of us, if not most of us, would never consider doing what Tom is doing in "Contents of the Dead Man's Pocket," but most of us have probably done other foolish things in our lives and know how it feels to be involved in something we knew was a mistake from the beginning.