I see it has IOS to 6400 so that's will be something I will need to read up on
Judging a camera's low light performance by looking at the ISO settings is like judging a car's top speed by looking at the speedometer. Actually, it's worse than that, since the numbers on the speedometer relate to physical measurements. Maybe a better analogy is the dials on a guitar amplifier. Some people, like the musicians in
Spinal Tap, are impressed if the numbers go to 11. Most are not.
The reason why the ISO setting doesn't mean much is that the shadow noise at the highest ISO setting is entirely up to the camera manufacturer. The only thing that's keeping the max setting from hitting seven digits is self-imposed restraint on the part of the people who designed the camera. To add insult to injury, there is no universal, must follow, standard as to midtone values in raw files versus light levels and exposure at any given ISO, leading some manufacturers to be conservative in that regard, and some to be, shall we say, optimistic. In the M240, Leica is on the optimistic side. I don't know about the S series.
Jim