'Leo Rising' by Paul Ruditis

The Power of Three has gone underground
Clues and magic can't be found
Grown-up sons, come quickly forth
Help your father find his worth

While a newly mortal Leo is out for a walk with Wyatt and newborn Chris, demons trap the Charmed Ones in the house and take them to the Underworld, where they are imprisoned by demon scientist Dr. Gnivik, who plans to steal the Power of Three. When Leo returns to find the house empty and in even more disarray than when he had left, he tries to piece together what happened, but can't. Due to his recent fall from grace, the Elders ignore his calls. What is he to do? With no other options and no magic of his own, Leo becomes desperate.

Using a spell from the Book of Shadows, his sons' magic, and a sliver of unicorn horn, he calls the future versions of Wyatt and Chris back to the present. Together, the Halliwell men go in search of The Charmed Ones. With Dr. Gnivik nearing success and the sisters powerless to stop him, it's up to Leo and the boys to save the day....

Published by: Simon & Schuster New York

Notes:
*Featuring Piper, Phoebe, Paige, Leo, Wyatt and Chris