These deadly games
(Book)

Crystal Donavan gets a message on a mysterious app with a video of her little sister gagged and bound. She has only 24 hours to play-- and win-- the kidnapper's game. At first the tasks are bizarre: steal a test and stuff it in a locker, bake brownies, make a prank call. Soon Crystal realizes each task is meant to hurt-- and kill-- her friends. But if she refuses to play, the kidnapper will kill her sister.Making impossible choices between her friends and her sister, Crystal must uncover the truth and find a way to outplay the kidnapper... before it is too late. -- adapted from jacket

Soon after receiving an anonymous message stating that she has twenty-four hours to play a game by the sender's rules or he will kill her sister, sixteen-year-old Crystal Donovan realizes that cooperating will destroy her friends' lives and she must figure out a way to beat the kidnapper at his own game before she loses everything.

Ages 14-18.,Wednesday Books.