Killing Time: Physics, Lust and Greed Series, Book 3

At every crossroads he has encountered in life, Sean Brody has made the safe choice. In the year 2046, at the age of ninety-three, Sean is given one final opportunity to deal with his greatest regret. Sean is the only man Marshall Grissom and Marta Hamilton can find who might be able to save Sheila Schuler, their friend and fellow traveler lost in the distant reaches of time. If Sean accepts the task of traveling to his childhood in a parallel universe-with no guarantee that any aspect of the past can be changed-Sean must also accept his death in the only world he knows.