It appears to me that one must start with a truth and then let the imagination take over to be able to write a fictional story.
One starts with a true fact and then the question – What if something else happens and so the story is formed to suit your purposes.
One cannot start a story from a vacuum, an empty sky, a place where nothing is happening or from an empty mind.
If there is nothing that excites you, you have to research something that captures your imagination, even if it is murder, because crime is what you like to read and therefore write.
Nicholas Evans researched ‘the History of Wolf Slaughter in America’ to be able to write his fictional story called ‘The Loop’. Without research of the true facts, this story could not be believed. And that’s what a fictional story has to be.
The same with Jeffrey Deaver’s ‘The Coffin Dancer’ or The Bone Collector’. He wanted his detective to be a quadriplegic. Deaver’s research into quadriplegia was painstaking and he even tried out the equipment himself.
In the end it is an invented story, but there are truths interwoven into the fabric or it wouldn’t be believable.