Easily one of the ten best movies of the 20th century. In Cold Blood is brilliant in the simplicity and realism of its storytelling, and absolutely riveting.
Robert Blake walks away with the film. The story seems to be presented almost entirely from Perry's viewpoint, despite Dick being the leader and planner of the pair. The viewer will invariable perceive Dick as being more unstable, immature, and generally feel like Perry would not have been pulled into this nightmare but for Dick and his need to be somebody and pull off a big score.
Based on a true story with particular attention to accuracy, In Cold Blood depicts the story behind the brutal and senseless murder of a rural Kansas family one cold, windy night, because Dick has bought into an age-old rural myth about prosperous farmers having a safe full of cash in their home. As "prosecutor" (a character that isn't given a name in the script), played by Will Geer, so astutely points out, their lives are bought for only $10 a head. Director Richard Brooks wisely chooses not to share with us the gruesome details of the murders until the end of the film, prior to this we only know it has happened and watch the lives of Dick and Perry slowly unravel as they attempt to escape not only being apprehended by law enforcement, but also Perry's own ever-escalating sense of impending doom. He repeatedly makes remarks, "No one ever gets away with a thing like that," and "I can't help thinking we left something behind that belongs to us." Dick is neither mature nor moral enough to feel any compelling sense of guilt over their crime, only irritation at Perry's. Indeed, after they are caught, it is Dick who breaks first, and suddenly faints when finally confronted with irrefutable proof that places the two men at the scene of the crime. I felt somewhat sorry for Perry from the very beginning of the film, and more-so as events progressed, but I only loathed Dick.
The genius of the film is the engaging manner in which the story is played. We do not for a moment think we are watching actors portray characters, but that we are watching the actual participants and events as they occurred. The story is unrelenting, taunt, the run time slightly in excess of two hours feels more like just a few minutes.
For those of you who are interested in such things, I noticed a couple of the "Goofs" listed here on the IMDb page for In Cold Blood are incorrect or exaggerated. Such as the "reversed" process shot, at the beginning of the film, as Dick and Perry are driving across the bridge into Kansas. To begin with, this isn't even a process shot, the camera is actually positioned in the backseat and the image you see beyond the windshield of the car is real. A large cargo truck located to the left front of Dick's Pontiac creates the optical illusion that they are going backward because it is traveling at a greater rate of speed, but closer examination will reveal that they are indeed going forward and it is an actual shot filmed from a moving vehicle.
As I previously stated, this is one of the ten best works of 20th century cinema, not recommended for the very young due to some course language and implied and inferred violence (no actual in your face gore as a modern film would resort to), but a thoroughly excellent film.

(Spoilers galore) This is an absolutely awful film. First of all it has that guy from medium. I guess he's made a career out of playing super doting dads. It was OK the first time he tried to scare his son by pretending to be a monster...but then 10 minutes later they cloyingly did it again! And so it goes, this film moves in excruciating real time. At one point, I started imaging it was days later, until I was reminded that the story line was only at the next day...in the early afternoon still! I'm not really sure who this couple is supposed to be in real life. First of all they are presented as sort of a Manhattan yuppie couple who grew up and had a kid. But they drive an old blue Volvo. Those types stopped driving Volvos decades ago. Today they drive Priuses. But in 2002, I'm sure they still weren't driving Volvos.
OK, then there's Wendigo. A "mysterious Indian man" gives the boy a little magic Wendigo statue and tells him of its powerful magic. C'mon...are we still doing ancient Indian mysteries. Just to drive it home, they pan across every Indian statue in their tourist trap upstate New York town. American Indians are portrayed in a manner not seen for decades in this film! Oh, and about Wendigo. He is not actually the cause of the horror. He doesn't kill the kid's dad which is the most horrible thing in the film...he's just killed by an ordinary hick with a grudge and a high powered rifle. The Wendigo only comes out late in the film to avenge the guy who killed the dad...oh, but wait, it seemed earlier that Wendigo was kind of mad at the dad, maybe because he killed a deer...so then Wendigo must have been happy that the dad was killed...but...
And so it goes...insulting, boring and nonsensical. There is no reason to watch this film at all.