Memory is the residue of thought. — Daniel T Willingham
Things get left behind — in floods, storms, restaurants, relationships, and apartments — and everything left behind tells us a little bit about the people and events that went before.
Write about an item left behind by a character. What can you show us about its previous owner? What details will lead the reader to make a strong connection between the two?
What past event has left a “residue” on your character? Are they aware of it? Do they see it clearly?
What residue/left behind item does your character misinterpret in your story? What do they think it means? What does it really mean?