Ada, Iggy, and Rosie are ready for the most super sleepover ever. They've got their sleeping bags, pajamas, a moon nightlight, and a dino-snore machine (well, that last one may not be perfect for the sleeping part of the sleepover!). This will be Iggy's first sleepover at his house, so his dad helps brainstorm ideas for what to do at the sleepover. They can play games like ping-pong, eat yummy popcorn, and even tell spooky stories! They want to start with a game of ping-pong, but the ping-pong table is in the basement—and Iggy warns them that the basement is haunted...or at least he thinks it is. But he's never actually gone down there because it's too spooky. It's up to the Questioneers to get to the bottom of if the basement is actually haunted by ghosts by using the scientific method, their bravery, and a whole lot of teamwork.