Cover of 'Time and Again' by Jack Finney
Time and Again is told in the first person by Simon Morley, a 28-year-old artist working in a 1970's Manhattan advertising agency who is approached to join a covert government operation exploring the possibility of time travel. Recruited as having the right stuff, Si begins to learn about the project and its goals.
Initially recruited to explore San Francisco prior to the 1906 earthquake, Si manages to convince his superiors to allow him to investigate 1880's New York. Simon's motive for choosing New York is to witness the mailing of an envelope. An event Simon hopes may explain a family mystery of his girlfriend Kate.
Unlike most covert projects involving time travel, this one does not involve any hi-tech machinery. Quite the contrary, the project director Dr. Danziger believes that the past is just outside the window and that you only have to free yourself from the present to step into it. Through mental conditioning, such as familiarizing the candidates with the past and through self-hypnosis, Dr. Danziger plans to project his subjects into the past.
As Simon becomes more adept at his training he eventually steps into the past and begins an adventure of a lifetime.