The Invisible Inc. gang is on a mission! They are working hard making computer greeting cards to raise enough money to invite their favorite author, D. B. Spooks, to visit their school. But when the class goes online to send the invitation, terrifying messages start appearing on the school computer screen. Who is sending these spooky threats, and are they coming from inside the building? Justin, Charlene, and their invisible friend Chip must team up to unravel the clues and discover the true identity of the mysterious chatter. Join the clever trio in this high-tech mystery full of suspense and fun!