A Pair of Docks by Jennifer Ellis

Fourteen-year-old Abbey Sinclair likes to spend her afternoons in the physics lab. But her practical scientific mind is put to the test when her older brother, Simon, discovers a mysterious path of stones that allows them, along with Abbey’s twin, Caleb, to travel back and forth between their world and what appears to be the future.

Unfortunately, they’re not the only ones who know about the stones, and they realize their lives are in danger from a man known only as Mantis. Abbey, Caleb, and Simon must follow a twisting trail of clues that lead them from their neighbor with Asperger’s to a strange professor who claims to know the rules of the stones… and to multiple futures.

It will take all of Abbey’s analytical skills to unravel the secrets of the stones, uncover the threads that tie the futures together, thwart Mantis’s plan, and keep her family alive—now and in the future.