Altar of Shulaani. The Altar of Shulaani, #1

Mike has a talent for falling into trouble. This time, he has fallen through time itself. When a beam of noon sunlight focuses on an ancient altar during his father's desert expedition, Mike leans in just a little too far. One moment he is part of an archaeological dig between Egypt and Libya. The next, he is thousands of years in the past, in a lost civilisation ravaged by plague, with chanting priests on one side and a jungle full of silence on the other.
Then he rescues a girl from the altar knife. Alinea is not from Earth. She is an alien, her parents dying in suspended animation aboard a hidden spaceship, and she needs Mike's help to reach them before it is too late. Between them and any hope of survival stand the Kloog: scaled predators with blazing red eyes and sharp curved claws, who arrived following a comet and have no interest in leaving peacefully.
With only his wits, a telepathic bond with Alinea, and a scaly beast named Beeper who eats trees and deflects weapons with his scales, Mike must find his way through jungles, ancient temples, and impossible odds to reach the one door home, if it ever opens again.