Dr. Albert Snowden, and his niece, Emily, experience this while traveling on Evaran’s temporally shielded space-and-time traveling ship. What they discover is that humanity has taken a different path, one that has made Evaran decide to interfere and change human history.
Discovering what caused the change is one issue. Dealing with the nonhuman factions in Earth’s past is another.
To make things worse, Dr. Snowden has to deal with a personal issue. It does not help that Emily is on a prison planet where she must survive, alone. Evaran, along with some new allies, must deal with both of their problems on top of an age old enemy.