Six-Word Sparks II: Mysteries

Six-word sparks are those magical mini-phrases that I use to capture the essence of an adventure idea in order to save it for later.  Sort of like reducing a sauce in cooking; the more water you boil out, the stronger the remaining flavor.

My first batch were pretty varied—a bit of politics, a bit of banditry—but this time I'd like to focus on mystery ideas.  These sparks may not turn into mystery adventures, but they'd all start with a mystery.

Six-Word Mystery Sparks

1. Birds, thousands, flock to ancient lake.
2. Farmer's barn fills with grain nightly.
3. Giant gears uncovered below city catacombs.
4. High-profile silver robberies throughout city.
5. Innkeeper disappears; wife scared, daughter suspected.
6. Local murder; only suspect?  The victim.
7. Local woodcarver deaths connected by forest.
8. Mighty river dries up; Gnomes accused.
9. Stone wall appears around city overnight.
10. Well begins drawing up green slime.