With their trip to Kroon behind them, Mateo, Tina, Booker, and Jennica are back on Earth, Elvis the dog is no longer missing, and all is safe and sound...right?

Wrong! Hot on their tails are Grunthar and his motley alien crew. NoWay and Clorox have made their way to Earth, too, ready to help the kids against whatever Grunthar is planning. Tina is determined to be the hero this time, but will she be able to figure out what the alien inventor is up to before it's too late?

Author Bruce Hale and illustrator Luke Séguin-Magee have crafted another rollicking tale featuring extraordinary black-and-white illustrations throughout.