Some Like It Hawk: A Meg Langslow Mystery by Donna Andrews

I love Meg Langslow mysteries.  They are full of fun in a crazy town filled with lots of family and friends.

Meg Langslow is plying her blacksmith's trade at “Caerphilly Days,” a festival inspired by her town’s sudden notoriety as "The Town That Mortgaged Its Jail." The lender has foreclosed on all Caerphilly's public buildings, and all employees have evacuated —except Phineas Throckmorton, the town clerk.

Mr. Throckmorton's siege has only been possible because of a pre-Civil War tunnel leading from the courthouse basement to a crawl space beneath the bandstand.
But the lender seems increasingly determined to evict Mr. Throckmorton—and may succeed after one of its executives is found shot, apparently from inside the basement. 

Meg and her fellow townspeople suspect that someone hopes to end the siege by framing Mr. Throckmorton. Unless the real killer can be found quickly, the town will have to reveal the secret of the tunnel—and the fact that they've been aiding and abetting the basement’s inhabitant.