of demonstrating that he is standing in a doorway because he can't very well light a cigar or smoke it out in the rain. When he lights the cigar he reveals that he is the man wanted by the Chicago police. So Jimmy refrains from introducing himself to his old pal and lets him do most of the talking.

O. Henry makes Jimmy seem like just another uniformed beat cop simply by describing an ordinary beat cop.

Trying doors as he went, twirling his club with many intricate and artful movements, turning now and then to cast his watchful eye adown the pacific thoroughfare, the officer, with his stalwart form and slight swagger, made a fine picture of a guardian of the peace. 

The ironic thing is that Jimmy really is patrolling his own beat--which just happens to be where he plans to meet Bob at 10 p.m. He is a bit early, so he does what he always does, which is mainly trying shop doors to make sure they are securely locked. Bob pulls out his ornate pocket watch.

“Three minutes to ten,” he announced. “It was exactly ten o'clock when we parted here at the restaurant door.”

This dialogue is to inform the reader that Jimmy is early, which explains why he was trying doors along the way and taking his time about getting to the rendezvous. It also informs the reader that the appointment is for ten o'clock. If Bob says he will wait a half-hour longer than that for his friend to arrive, then Jimmy knows he has until ten-thirty to get someone to make the arrest which he doesn't care to make himself.

Incidentally, the "handsome watch" with the lids set in small diamonds is one of the things by which Jimmy identifies Bob as the man wanted by the Chicago police. They sent a "wire," a telegram, in which they provided as much of a description of 'Silky' Bob as possible. Photos or even sketches could not be sent by wire. They also included two other things Jimmy saw when Bob lit his cigar.

The light showed a pale, square-jawed face with keen eyes, and a little white scar near his right eyebrow. His scarf pin was a large diamond, oddly set.

The setting for the large diamond would have been described in more detail in the telegram. Since Bob never gives his name, O. Henry would have to provide other means by which Jimmy could be sure the man in the doorway was really his old pal and really the man wanted in Chicago. Bob doesn't introduce himself by name because that would have pretty much forced the cop to do the same. And if the cop didn't introduce himself, that might have made Bob suspicious--in which case he might not have been standing there when the tall plainclothes detective showed up at around twenty minutes past ten.

The policeman, Jimmy Wells, is impressive in two ways: as a friend and as a professional. As a friend, he shows just how much his friendship to Bob means by turning up at the exact time at the exact place at which they'd arranged to meet all those years before. Although Bob is a thief and Jimmy is a cop, Jimmy still clearly values his friendship after all these years. That explains why he doesn't want to subject Bob to the indignity of being arrested in person by his old pal. He leaves that to a detective.

On a professional level, Jimmy is impressive for the way he goes about his work. Despite his long-standing friendship with Bob, Jimmy is still a cop, and his overriding duty is to uphold the law. It would have been all too easy to let Bob slip away for old time's sake, but Jimmy does the right thing and helps to bring about his friend's arrest.

The policeman on the beat is made to appear like a typical beat cop in a NYPD uniform. His actions are described, but there is no description of his physical features. O. Henry is adroitly introducing a major character, Jimmy Wells, without actually identifying him. The reader will believe that he stops to talk to Bob because it is just part of his routine to check out anyone who might seem a little suspicious. Bob knows he looks a little suspicious standing in a darkened doorway. He had an appointment to meet his old friend at that location, but he thought it would still be "Big Joe" Brady's restaurant. As the policeman tells him, that restaurant was torn down five years ago.

O. Henry describes the unidentified cop in such a way as to suggest that he has been a beat cop for a long time. The way his handles his billy club suggests that he has been twirling it for many years. 

Trying doors as he went, twirling his club with many intricate and artful movements, turning now and then to cast his watchful eye adown the pacific thoroughfare, the officer, with his stalwart form and slight swagger, made a fine picture of a guardian of the peace. 

Saying that the officer "made a fine picture of a guardian of the peace" is another way of saying that he looked like a typical uniformed beat cop. He is trying doors of closed shops because this is part of his usual routine. The words "stalwart form" suggest that he is overweight, like many beat cops who are approaching middle-age.  O. Henry takes pains to make Jimmy Wells look like a typical cop, so that the reader will have no suspicion that the cop is actually keeping an appointment made twenty years ago and that he is the very man Bob has come a thousand miles to meet.

O. Henry specifies that the streets in the neighborhood are dark because almost all the business establishments have closed for the night. Bob will not be able to recognize Jimmy Wells for several reasons:

• It is dark.
• He wouldn't have expected Jimmy Wells to be a cop in uniform.
• He hasn't seen Jimmy in twenty years, and Jimmy has naturally changed. He was a young man when he and Bob parted; now he is forty years old.
• When Bob lights his cigar it illuminates his face, but the match is between him and Jimmy. Instead of making it easier to see Jimmy's face, the lighted match actually blinds Bob, so that he can only see a vague figure in a dark uniform.

Jimmy intended to introduce himself, but Bob started talking and didn't give his old friend a chance to speak.

"It's all right, officer,” he said, reassuringly. “I'm just waiting for a friend. It's an appointment made twenty years ago. Sounds a little funny to you, doesn't it? Well, I'll explain if you'd like to make certain it's all straight." 

Bob lights his cigar and Jimmy recognizes him as the man wanted by the Chicago police. He decides not to introduce himself after all. The two men have a short conversation. We can imagine that Jimmy is privately wondering what he should do. He makes the decision to go back to the precinct station and get some other officer to make the arrest. Bob would never have known that the cop he had been talking to was his old friend Jimmy Wells had not Jimmy given the arresting plainclothes officer a note to pass on to Bob when the arrest was made.

Bob: I was at the appointed place on time. When you struck the match to light your cigar I saw it was the face of the man wanted in Chicago. Somehow I couldn't do it myself, so I went around and got a plainclothesman to do the job.  JIMMY.

Just like Bob, the reader has been thoroughly taken in by O. Henry's clever storytelling and is just as surprised as 'Silky' Bob.