Your players will ignore your plot and adopt the shopkeeper. Plan for it.
I spent two weeks building a villain with a tragic backstory and a three-act arc. My players spent the entire session helping an NPC innkeeper I improvised — they renovated his kitchen, found him a business partner, and named the inn.
The villain has now been waiting in his tower for four sessions.
GMs of frontpage: what did your players latch onto that you invented in five seconds of panic?
a goat. i gave a random farm a goat for flavor. the goat has a name, a backstory, and a higher survival priority than two party members