These rich Great Falls fires are always suspect. This one started at 9:45pm and investigators are still looking for the cause.
If you remember, the last big fire in Great Falls started a long arson trial after it was noted that house was getting ready to be sold at auction.
Here's the story of the last Great Falls house fire -
https://www.greatfallstribune.com/story/news/crime/2018/04/19/daniel-doran-arson-case-great-falls-home-insurance-payments/533367002/