Echoes of the Past (Demon Squad, Book 4)

An unexpected message gives Frank the answer he's sought for years--Where did God and Lucifer go?--but the knowledge brings its own dilemma as inter-dimensional war looms, threatening to engulf the Earth.

Tasked with the planet's defense, Frank scrounges for a plan and finds a piece of his past better left behind. If the aliens don't kill him, what he learns just might.