First printing with complete numberline; 2nd state with error on p. 300 corrected. Tight, clean, flat, square, sharp and crisp book in DJ with wear, small tears, and wrinkling at the edges. Pages modestly toned. 

When a stranger attempting to deliver a cryptic message is shot dead at his table, Dr. Richard Ames is thrown headfirst into danger, intrigue, and other dimensions, where a plot to rescue a sentient computer could alter human history... 

Like Heinlein himself, main character Richard Ames is an ex-military man turned writer who fancies himself a pundit. An assassination attempt precipitates his marriage to Gwen Novak and sends the newlyweds scurrying to the Moon and then to the planet Tertius, headquarters of the Time Corps.