The Sherlock Society by James Ponti

Siblings Alex and Zoe Sherlock take their last name as inspiration when choosing a summer job. After all, starting a detective agency has to be better than babysitting (boring), lawn mowing (sweaty), or cleaning out the attic (boring and sweaty). Their friends Lina, an avid bookworm, and Yadi, an aspiring cinematographer, join the enterprise, and Alex and Zoe’s retired reporter grandfather offers up his sweet aquamarine Cadillac convertible and storage unit full of cold cases.

The group’s first target is the long-lost treasure supposedly hidden near their hometown Miami. Their investigation into the local doings of famed gangster Al Capone leads them to a remote island in the middle of the Everglades where they find alarming evidence hinting at corporate corruption.