Shattered Rainbow

This is an Apple Books audiobook narrated by a digital voice based on a human narrator.

Five friends dare to set out on a 20-mile hike across the Utah Dinosaur National Monument's desolate expanse in August of 2000, but a freak snowstorm causes tragedy to strike.  One of the five breaks his arm.  Another is seriously injured when he falls into a cavern once populated by an ancient people whose relics remained hidden and protected for more than sixty-one thousand years 

During the rescue of the injured man, Derek Cousins takes a look around the cavern and discovers the relics.  What he does next sets in motion a series of events culminating in murder.  And then Derek disappears.

The author begins the story by switching back and forth between the present and sixty-one thousand years ago when the ancient people walked the earth.  He continues the pattern in Part II by switching between the original story and three years later when the murder case is transferred to the DA's office in Craig, Colorado, not far from where the murders occurred.

In the end, greed and murder combine to create an intriguing story around the relics of an ancient people.