Plotting (my own downfall)

The writing course I am attending has forced me to think seriously about plotting out the events for my latest writing project. You might think that's stating the obvious, or ask why would you be trying to write a novel without having spent time working out the plot etc?

The only feeble excuse I can offer is that while I had ideas for a new novel, I hadn't really got beyond the pondering stage, but I then took my ideas to the course to use as a framework for a novel, whereupon I realised part of the course requirements were to develop and submit a synopsis.

I have the first four chapters of the novel written, subject to a total re-write at any moment of course, but I realised that during the course of the classes I am bound to be asked about details of the novel which I haven't given much/any thought. So I sat down and tried to work out the what my characters were trying to achieve and how they were going to do it.

To start off with, all I had was a bunch of unconnected scenes and snatches of dialogue and a rough through-line. Somehow I needed to interlink them into a meaningful narrative. I'm not sure if the task was made harder by the fact that I am planning to write a crime/noir/ thriller novel, so the plot and all its interdependent strands have to reach a neat or at least satisfying ending.

In a previous attempt to get my head around the plot, or lack of, I tried to talk it through with my wife. That didn't help, to be honest. At the end of it I'm not sure who was the more confused, me or her. I've also found that once you give serious thought to the plot developments, it interferes with previous ideas or renders previously written chapters irrelevant, but this all part of the maddening yet exciting writing process.

On that note, if anyone has interesting and helpful suggestions of how you approach the plotting of a novel, I'd be interested to hear it.

PS: the photo is not mine, I found that on google images, but that's kind of what I'd do if I was organised!