Lost in Time is the follow up to the Reversione series of novels. The family that reset the future are now trying to recover a ship lost in time in the past. 

When a ship built for exploration explores the center of the galaxy, an accident results in the ship displaced in time. Diane and William are brought in to help find that lost ship and then help the members of the crew from that ship build a time machine and send the ship back to the present. Along the way, the two learn more about the future than they had ever known. Love keeps them together when they reset the future. Now love will keep them in the adventure in the past to restore the future.