In the prologue, Adrian "Shel" Shelbourne is being buried. His family, some of his cow-orkers, his friend Dave, and his almost-girlfriend Helen are there at the cemetary.
When the story starts (before the prologue), Shel finds that his father, Michael, has disappeared. Michael is a noted physicist and had told them he'd be somewhere else for a few weeks of work, but he wasn't there. After some weeks, Michael's lawyer calls Shel and gives him an envelope that Michael had left for him if he disappeared or died. Shel opens the envelope to find what turn out to be Q-pods.
He finally figures out the password for a Q-pod and is then prompted:
DO YOU WISH TO TRAVEL?
[more blanks to narrow destination]
Now, Shel started out in physics, but when he sees that, he doesn't think of time travel (or space travel). He answers, pushes the button, and turns up somewhere else, quite confused. He calls his friend Dave to come get him. It's the next day when Shel figures out what happened, what the Q-pods are, and the basic method of using them.
As the book progresses, they not only search a lot of prominent events in the past, trying to find Michael, but figure out more advanced ways to use the Q-pod. They both find ways to make money and have other homes. But is Shel really dead or not?
This is a much lighter book than his others, and I felt like I was constantly ahead of the characters. I like to be surprised sometimes.