(topic: Combinations) - Hacker finds the Krystal of Kalmoor, the powerful orb that will give him eternal power. By possessing the Krystal, Hacker can roam cyberspace and create havoc without having to recharge his power. When the kids and Digit arrive to retrieve the Krystal, they are stymied by a series of switches, levers and buttons. Faced with the challenge of too many choices, the kids discover the value of lists, tables and, yes, tree diagrams! The Big Idea: Overwhelmed with choices? Lists, tables and tree diagrams help you master the combinations.