The Wild Warning (Melody Lane Mystery Stories)

Carol's younger sister and their cousin, both of junior high school age have found a robber's cave hide-out. Carol discounts their story, believing their discovery to be a boys' play area. She is caught up in another strange affair at the local drugstore, which is a substation for the Post Office. A registered package disappears while Carol is actually at the store. The only person they saw enter the building at that time is a very poor girl who is always eager to work for a few extra pennies. The sender of the package chooses not to press charges. But who took it, and why, and why is the beautiful young clerk so nervous?