Who is Alex Hunter from The Key to Midnight and what is their importance?

Alex Hunter is a private detective who built a multi-million dollar security firm from the ground up. Alex has grown bored with his life and is on a month-long vacation in Japan when he happens on the Moonglow Lounge in Kyoto. At the Moonglow, Alex becomes fascinated with the headliner and owner, Joanna Rand. As Alex watches Joanna perform each night, he feels as though he knows her from somewhere. Finally Alex realizes that Joanna is a dead ringer for the missing daughter of an American senator, a case he worked himself over a decade before. Alex takes Joanna to lunch and asks leading questions, trying to figure out how she came to be in Japan if she really is this missing girl. Finally Alex calls her by the name of the missing girl, Lisa Chelgrin. Joanna has no idea what Alex is talking about.