i dont know in book 1 they all get together in after there adventures or if this is the start of there adventures.
any how during the books each of the kids go back to a time were they find clues as part of a bigger mysterie.
there are 2 treatments, first in book 5 were 1 of the girls get tied up and in book 7 when all of the kids get there hands tied behind there back(7 kids, 3 boys(the ones with headgear) and 4 girls(red head, blond pink ribbon, punk/goth and the one that got a treatment before)
Book 5

Book 7
