Who fingered Ole Andreson?

The kind of writing that can be done. How far prose can be carried if any one is serious enough and has luck. There is a fourth and fifth dimension that can be gotten.
Ernest Hemingway, Green Hills of Africa
The two hit-men assume that Ole Andreson will arrive at Henry's Lunch Room at six o'clock:
"I'll tell you," Max said. "We're going to kill a Swede. Do you know a big Swede named Ole Andreson?"
"Yes."
"He comes here to eat every night, don't he?"
"Sometimes he comes here."
"He comes at six o'clock, don't he?"
"If he comes."
"We know all that, bright boy," Max said. "Talk about something else."
Obviously these killers have gotten their information from the "friend" who sent them. But where did the friend get the information? And why was it only partially correct? He must have gotten it through someone living in Summit, and that informant must have assumed incorrectly that Ole ate at Henry's every night when he only ate there almost every night. Chances are that the friend did not come to Summit in person but heard through the grapevine that Ole Andreson was living in the town of Summit. So he sent someone to check it out. That man returned with the information that Ole was definitely living there and ate at Henry's Lunch Room every night at six.
After George unties Nick and Sam, Nick goes to Hirsch's rooming house, where he gets involved with the inquisitive Mrs. Bell. This needy, gossiping, lonely woman waits for Nick by the front entrance and then starts talking about Ole:
"He's been in his room all day," the landlady said down-stairs. "I guess he don't feel well. I said to him: 'Mr. Andreson, you ought to go out and take a walk on a nice fall day like this,' but he didn't feel like it."
"I'm sorry he don't feel well," the woman said. "He's an awfully nice man. He was in the ring, you know. . . . You'd never know it except from the way his face is. . . . He's just as gentle."
Mrs. Bell takes great interest in Ole. Even though he has stayed in his room all day, she has found some excuse to get inside to ask about his health and advise him to take a walk. Her words, "He's just as gentle," betray that she is in love with this big, gentle, and unattached man. She knows more about his comings and goings than anybody else in Summit, and she is more than willing to talk about him with any stranger. Hemingway establishes that Nick and Mrs. Bell are strangers by having him mistake her for Mrs. Hirsch.
The most likely scenario is this. The friend sent an agent to verify the information about Ole. The agent easily learned that Ole lived at Mrs. Hirsch's rooming house. Mrs. Bell answered the door. The friendly caller inquired about rooms and rents, then asked if there were any boxing matches held in Summit, or some such leading question. This would immediately prompt the bell-shaped, middle-aged woman to bring up her favorite topic, the ex-boxer living right under her own roof. During the conversation the agent would have been told that Ole ate dinner at Henry's Lunch Room every night at six o'clock. Mrs. Bell might have asked the caller if he would like to meet Mr. Andreson, and the caller would have said something like: "Oh, no! I wouldn't want to bother him. Maybe I'll run into him at Henry's."
This would explain the rather strange initial meeting between Nick and Mrs. Bell:
"Is Ole Andreson here?"
"Do you want to see him?"
"Yes, if he's in."
Nick followed the woman up a flight of stairs and back to the end of a corridor. She knocked on the door.
"Who is it?"
"It's somebody to see you, Mr. Andreson," the woman said.
"It's Nick Adams."
"Come in."
Here is a landlady in a cheap small-town rooming house personally escorting a visitor up a flight of stairs and down to the end of a corridor to announce him when she does not even know his name. She would certainly not do that for anyone but Ole. She takes any opportunity to talk to him. Notice the exasperation in Nick's voice when he says, "Yes, if he's in." Why would he be asking for him if he did not want to see him? But she has gotten the impression from the "friend's" agent that some people ask about Ole when they do not want to see him.
After talking to Mrs. Bell that afternoon, the agent would have stopped by Henry's Lunch Room at six o'clock and would have seen a big Swede with a marked-up face eating the special dinner at the counter at exactly six o'clock; and he would have carried that information back to Chicago.
But why did Mrs. Bell think Ole ate dinner at Henry's every night at six, when he obviously only eats there at six when he eats there—which is clearly established by the vital fact that he does not show up on the night the killers are waiting? There is an obvious answer. Mrs. Bell is badgering Ole, but he is too nice a man to hurt her feelings. She is always concerned about his health and frequently offers to bring him a bowl of her homemade chicken soup and a slice of her homemade apple pie—or whatever. She must know he is in the habit of taking long walks on days off, which is why she suggested he take a long walk today. If he goes for a walk on a Sunday, he is sure to run into her in the foyer when he returns, and she is sure to ask him if he had anything to eat. He always tells her he ate at Henry's because he does not want her bringing him her chicken soup and apple pie. He does not want to get involved with her, but she certainly wants to get involved with him. So this is how she got the idea that he eats at Henry's every night at six when he probably does eat there every night at six—except on Sundays when he has not been working hard enough to build up an appetite. He only tells her he ate at Henry's on Sundays.
So it was Mrs. Bell, the lonely widow who is in love with Ole Andreson, who is responsible for bringing the killers to Summit that Sunday night. She knows, or thinks she knows, all about his habits. She talks about him at church, when she goes shopping, when she visits friends, and whenever else she can. It was Mrs. Bell who spread the word which finally got back to Chicago and caused the friend to send his agent to Summit. And then it was Mrs. Bell who inadvertently told the agent where and when the killers would have the best opportunity to kill the big Swede.
Hemingway never wasted words or even punctuation marks. There are many clues in "The Killers" that can enable an intelligent reader to see a "fourth and fifth dimension" to the story. The fourth dimension has to do with time. The perceptive and thoughtful reader can see how invisible but tangible things that happened in the past are shaping the events dramatized in the present. The fifth dimension probably adds depth to the fourth dimension, making unrecorded events more cogent—but Hemingway never explained that aspect of his legendary "Iceberg Theory."