I've seen the film several times now, and I thought it might be interesting to reread the book and compare them. Neither book nor film pretend to be mysteries; but as I can't say much about them without discussing the whole plot, I'll put the rest after the break. If you haven't read the book or seen the film and you're planning to do either, then you'd better not read any further.
King's Ransom is the story of a kidnapping. The main character is a businessman, Douglas King, who has worked his way up to be the production manager of Grainger Shoe; the kidnappers target his son. There are two complications: the kidnappers mistakenly take the son of his chauffeur; and King's money is currently tied up in a deal he needs to win a boardroom battle that will see him either ruined or in charge of the company. The kidnappers learn that they have the wrong child, but still demand the ransom from King, so that he is faced with a choice of saving someone else's child at the cost of disaster for himself, or turning his back on them.
In High and Low the premise is the same. The main character is now GONDO Kingo (権藤金吾), played by MIFUNE Toshiro (三船 敏郎), and he's very similar to McBain's King, a tough, aggressive businessman, risen from the shop floor, taking pride in the shoes he produces. For the first third of the film (most of the book) the story follows the original remarkably closely. In particular the opening scene in Gondo's house, where the other board members try to persuade him to join him in ousting the current chairman is often nearly a translation of the corresponding chapter. This brings in good material, like a very effective speech where Gondo tears apart a sample of the shoddy shoes the other board members are planning to make.
"Well, all right," Stone said, "all right, that's just a sample you've got there. We can put out a slightly better shoe. Maybe something to—"In the negative column, the clumsy exposition line
"Something to what? This shoe'll fall apart in a month! Where's the steel shank in this? Where the hell are the counters? Where's the box toe? What kind of a cheap sock lining is this?" King ripped out the sock lining and then tore off the strap and buckle. With one quick movement of his hands, he snapped off the heel.
I represent sales, you represent factory, and Rudy here is fashion coordinator.also turns out to be in the original. The chief differences between the early parts of film and book are what Kurosawa has cut out. There's much less of the police investigation; and in the book we also follow the kidnappers, a group of three, whose internal divisions will lead to the boy's return.
But as we approach the point where the ransom must be delivered, book and film diverge almost completely. In the book, King refuses to pay the ransom, agreeing only to pretend to give in, so that the police have a chance to track the kidnapper. This is all the police ask in the film, after Gondo has refused once; but various factors (the entreaties of his wife and the boy's father and disgust at the success oriented manipulations of a former ally — an episode taken from the book) lead him to decide to pay anyway. In a scene symbolising his change of life, he hauls out his old shoemaking tools to stitch devices the police hope may help in discovering the money into the ransom bags. In the book, the kidnappers communicate with King's car by radio, with a clever set up that should insure that the police cannot follow. The trick works against the kidnappers, when the wife of one of them, an unwilling party in the crime, calls out over the radio to give away the plan, as she fears for the boy's life. In the film, Gondo is instructed to take a train and then receives a radio telephone call on the train instructing him to throw the money through the window at a bridge. (I hope you took in the warning not to read on if you wanted to see the film, because the first time you see it, this whole section is wonderfully full of tension).
At this point the book has come to its end, with the capture of the main kidnapper and the return of the boy. The film is only halfway; and the rest is all Kurosawa. The boy has been returned, but the kidnappers have got away with the money. Now the film turns completely into a police procedural. Kurosawa has even transferred here details he had dropped from earlier in McBain's plot (the identification of the car). The depiction of the investigation is engrossing; and there is added tension as the chauffeur independently takes his son to try and retrace the route, while the police close in on the same goal using the clues they have uncovered. When they discover the house where the boy had been held, it holds the dead bodies of the main kidnapper's accomplices, murdered through an overdose of heroin.
Throughout the investigation, Kurosawa gives us glimpses of the anonymous kidnapper in the decrepit housing below the hill on which Gondo lives. When the investigation finally closes in, we and the police follow the kidnapper through the harbour district (I think the setting is Yokohama), first to a bar with a juke box and dancing, then to the hangout of hopeless drug addicts. The style in particular of the latter scene is deliberately very different, abandoning the day to day realism that runs through most of the film. The earlier parts of the film have been in Gondo's air conditioned mansion or in normal public spaces. We have so far not seen much of the "hell" part of the title. The kidnapper ruthlessly tests the efficacy of the heroin by killing an addict, then sets off to the hideout. The police have tricked him into thinking his accomplices are still alive and are waiting for him there. We finish with two scenes: one where the police return the money to Gondo, too late to stop the foreclosure of the mortgage on his house and the auction on his property; then an intense final scene, again a break in style from the rest of the film, in which Gondo visits the kidnapper (who is awaiting the death penalty and has asked to see him), and hears from him of the hatred that had led him to target Gondo.
What are the key differences between film and book? I think, in McBain's world, no single character dominates. While King is the main character, every policeman, criminal and bystander has there own life and interests and the story that we read arises out of the interplay between them. In the film, only two of the police are much more than faces to us; and the film is very much Gondo's story. The latter half moves away from the Gondo household, but police and press talk repeatedly about what they owe to someone who has made such a sacrifice. (This sounds a bit like the contrast between an extremely individualistic view of society and a samurai view; but when I say that, I worry that I'm just following national stereotypes. It's not something I find in films by other Japanese directors.) The other difference is the emphasis on the hillside ease of the rich Gondo and its contrast with the poverty in the town below, the kidnapper's motivation. The contrast of King's neighbourhood with other parts of the city is emphasised by McBain; but this is more because the city is like a character for him, than for any thematic purpose. The final scene ties the two aspects together, we see Gondo's life and his enemy's together and the result of their choices.
One piece of showmanship in the film is the appearance in a black and white film of a pink cloud from an incinerator, as the ransom bags with the police's chemicals are burnt. According to the Japanese Wikipedia page on the film, this intrusion of colour into a black and white scene was something that Kurosawa had wanted to use for the key scene in his previous film Sanjuro (椿三十郎 Tsubaki Sanjuurou, 1962), where camelia drifting down a stream bring a signal to the hero's allies. The scene in High and Low works well enough, but the unrealised camelia scene would have been much more satisfactory. I wonder if anyone has digitally adapted the original to realise the idea.