O. Henry builds the suspense in this story by introducing the two characters, and then not letting you know who is who right away. They are two old friends who are meeting after twenty years, and he slowly feeds you details of their backstory. It later is revealed that one is a police officer and one is a crook, and the twist is that the police officer has been talking to the crook the entire time—and he didn’t know it! Neither does the reader, until the end.

In the beginning, we just see a very determined policeman seemingly walking his beat. His impressiveness is habitual. This means that he just can’t help it, because it is part of who he is by now. Duty and responsibility are ingrained in him. O. Henry is building suspense already, because that will be important later.

Then, in the doorway of a darkened hardware store, he sees a man with an unlit cigar. The conversation gets interesting. First of all, the man, “spoke quickly.”

"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?...”

There are many telling things about this encounter. A darkened doorway? An unlit cigar? The man’s quick reaction to the police officer? Warning bells should be going off in the reader’s mind—this is foreshadowing.

The mean tells a story about making an appointment to meet twenty years ago with a friend named Jimmy. He lights his cigar and his face—and a scar—are clearly shown.

Well, we agreed that night that we would meet here again exactly twenty years from that date and time, no matter what our conditions might be or from what distance we might have to come.

The interesting thing about this is that the cop does not react, other than to say it is an interesting story and ask if he has heard from his friend. Bob, the cigar smoker, comments that Jimmy will be there because “he always was the truest, stanchest old chap in the world.”

The cop leaves and another man, comes, pretending to be Jimmy. Bob says immediately that he has changed a lot. That is another signal to the reader that it may not be Jimmy after all. It builds suspense, because we do may not know what is going on, but we know something is not right.

"You're not Jimmy Wells," he snapped. "Twenty years is a long time, but not long enough to change a man's nose from a Roman to a pug."

After that, the cop tells him he has been under arrest for ten minutes! Then he gives him a note from the real Jimmy, who tells him that when he met him he knew he had to arrest him but did not have the heart to do it himself, out of friendship.

The twist in this story is that Jimmy did show up, all along, and he both did and did not arrest Bob. Ironically, Bob turned into a criminal and Jimmy into a cop. Jimmy wanted to do the right thing and the wrong thing at the same time, and found a way to do his duty and do right by his friend. O. Henry gives us little hints all along, leading up to the final twist. The unlit cigar and then the flash that showed Jimmy who Bob was and allowed him to recognize his friend as a wanted man, and the fact that Jimmy never acknowledged who he was, as well as Bob’s reaction to seeing a cop, all foreshadow the surprise ending.

Twenty years is a long time to keep a promise. As you can see, it really did not change the kind of person Jimmy was. He remained the loyal and honest, and dependable person Bob said he would be. Bob said he would be there, and he was. Bob said he could count on Jimmy, and he could.

How does O. Henry use foreshadowing, point of view, irony, and suspense to create an effective narrative in "After Twenty Years"?

There's not much foreshadowing in this story, but O'Henry drops a few hints that Bob might be a criminal, such as mentioning the scar on his face and the diamond studded watchcase he carries. O'Henry also foreshadows that the person who talks to Bob at the end is not Jimmy when Bob says:

You've changed lots, Jimmy. I never thought you were so tall by two or three inches.

The point of view is third-person omniscient, but the narrator chooses to withhold certain facts from the reader until the end, which adds to the surprise. The most important withheld fact is that Jimmy Wells is the officer who initially approached Bob.

O'Henry is famous for his use of situational irony, which is when events work out differently than the characters expected. The chief irony is that a reunion with his best chum that Bob looks forward to as a happy time becomes the occasion of his arrest. Another irony is that Bob looks down on Jimmy as a plodder and sees himself as a success story, but by the end of the tale, the tables have turned.

The suspense comes in wondering whether Jimmy will show up and what he will be like if he does.

How does O. Henry use foreshadowing, point of view, irony, and suspense to create an effective narrative in "After Twenty Years"?

The master of the ironic reversal, O.Henry creates in "After Twenty Years" a narrative that is both suspenseful and touching by utilizing other literary techniques, as well.

•  Foreshadowing

In the beginning of the story, the scene in which a policeman sees a man leaning in a darkened doorway, and the man in this doorway quickly explains his purpose for standing there, is an example of foreshadowing, or hinting at things to come in the narrative. Specifically, as this stranger explains who he is and why he is there, he lights his cigar, revealing a small scar under his eyebrow and a large diamond "scarfpin." These details of how the man in the doorway looks suggest that there may be a history behind this man.

Also, the fact that the policeman asks the man in the doorway if he is going "to call time on him sharply" ("After Twenty Years") hints that for some reason the policeman wants to know how long this man will remain there.

• Point of View

Point of view is closely connected to the suspense of the story because, while there is technically a third person objective narrator, the scene at the doorway is presented in the manner of an officer of the law who talks to a stranger, questions him, and then reports what occurs without any emotional or artistic interpretation. Later, in the scene in which Bob thinks that Jimmy meets him, the point of view remains third person narrator, but the style moves to the perspective of Bob. With this very limited point of view, suspense is effectively increased.

About twenty minutes he [Bob] waited, and then a tall man in a long overcoat, with collar turned up to his ears, hurried across from the opposite side of the street. He went directly to the waiting man. ("After Twenty Years")

Then, as Bob and the other walk together, the tall man walks under a street lamp, and Bob realizes that this man cannot be Jimmy. He is angered and fearful:

"You're not Jimmy Wells,...Twenty years is a long time, but not long enough to change a man's nose from a Roman to a pug." ("After Twenty Years")

So, to Bob's surprise, he is arrested. Then Bob is handed a note that he holds with a steady hand that starts to tremble as reads what his old friend Jimmy has written.

• Irony

The ironic reversal that Bob has become a criminal wanted in Chicago while his former best friend is a New York City policeman is given a certain poignancy because Jimmy does not have the heart to arrest his friend who has come hundreds of miles to reunite with him. 

• Suspense

Suspense in O. Henry's story is generated as the reader wonders if Jimmy will arrive and meet his friend Bob after twenty years. Then, when a man who is taller with a different nose from that of Jimmy appears, there is more suspense created.

Of course, the surprise ending that reveals the tenderness of a police officer who performs his duty is a result of the suspense created throughout the narrative. For, the identity of Jimmy Wells is not revealed until the very end of his letter.