Recall a recent museum visit and all the artifacts you saw there. Which were the most valuable? The most appealing? The ones you wish you owned?
Go online and search for images that represent things you might have seen. Print up one or two.
Imagine those artifacts disappearing, without a trace.
Your task is to write the story, beginning with your protagonist/antagonist strolling through the museum, taking careful looks at various items.
Take time to describe each, the character’s reaction to them, and let readers get into her internal thoughts. (This is tricky, but you can do it!)
Write what she does as closing time looms ever closer. Does she saunter out, to return another day? Does she hide somewhere so as to steal the items once the building is cleared?
How does she steal them, especially if they are under or behind glass?
Have fun with this one.