The Rose Queen by M. E. Rabb
(#1 in the Missing Persons Series)

Sam and Sophie Shattenburg are on the lam. They have changed their identities and run away to Venice, Indiana to avoid being separated by their uncaring step-mother, now that their father has died. Unfortunately a popular teenage girl is now missing and she was last seen with Sam and Sophie. With the Venice police being inept, it's up to Sam and Sophie to clear their own names without blowing thier cover.
A quick, light read but not fluff.

Highly Recommended