The ghosts of Tupelo Landing / by Sheila Turnage.

Enhanced descriptions from Syndetics:

Small towns have rules. One is, you got to stay who you are no matter how many murders you solve.


Miss Mo LoBeau - one half of the (probably) world-famous Desperado Detective Agency - is back! She and her fellow Desperado, Dale, went famous for about a week over the summer when they solved a murder in their hometown of Tupelo Landing - population 148 minus one (murder). Now sixth grade has started and it's back to being regular.
But regular doesn't come easy to a girl like Mo.
So when her beloved Miss Lana makes an Accidental Bid at the Tupelo auction and winds up the mortified owner of an old inn with an unidentified ghost in the fine print, Mo's itching to take the case. Plus, a historical ghost might make for some much needed Extra Credit in history. Who's haunting the old inn? And why? The Desperado Detectives set out to solve their second big case - only to find the inn might not be the only thing in Tupelo Landing haunted by the past.
With some unexpected help from slick new kid in town - Crenshaw, Harm Crenshaw (as in Bond, James Bond) - Mo and Dale discover the truth about a lot of things. Even themselves.
A companion to the New York Times bestseller Three Times Lucky .
Small towns have rules. One is, you got to stay who you are no matter how many murders you solve.
Praise for Three Times Lucky
' Mo is so plucky that young readers may wish she lived next door.' The Wall Street Journal
'An irresistible narrator - a literary descendant of Scout Finch of To Kill a Mockingbird .' Newsday, Top 12 Children's Books of 2012
* 'Mo LoBeau is destined to become a standout character in children's fiction.' Kirkus Reviews , starred review