If you have teens who enjoyed the Hardy Boys or Nancy Drew series, they will love ALL of the mystery novels by Joan Lowery Nixon (I admit to reading them all myself when wanting a great mystery I can finish in just a couple of hours).
about a girl named Abbie who has to take care of a crabby old lady who name is Edna Merkel.
The lady is going after crooks.
But when her big mouth get her in trouble.
The Abbie has to fingure out who landed Edna in the hospital.