Central to the murder plot is the fascination which Laura holds for the male characters in the movie, especially the three with the most screen time: Lydecker, Carpenter, and McPherson.
McPherson's growing obsession with Laura is all the more effective because he is normally a reserved, self-contained man who is definitely not the romantic type. For example, when Lydecker asks him if he's ever been in love, he answers laconically, "A doll in Washington Heights got a fox fur out of me once." Also, when Lydecker shows him Laura's portrait for the first time, McPherson glances up at it and says indifferently, "Not bad." This provides a dramatic contrast to the later scene in which McPherson is coming unglued, restlessly shifting in a chair, drinking and staring uncomfortably at the portrait.
'Laura' is an examination of twisted love and obsession as much as it's a murder mystery. It's also slick and stylish, inhabited by memorable characters, and enlivened with caustic wit and black humour. It almost doesn't matter in the end which of the suspects is the guilty party: nine tenths of the fun is getting there.
* The movie is based on the novelization of a play, 'Ring Twice For Laura,' by Vera Caspary.
* The character of Lydecker is apparently based on columnist and critic Alexander Woollcott. He must have been quite a colourful individual, as the character of Sheridan Whiteside in one of my favorite plays, 'The Man Who Came To Dinner', is also based on him.