Trail of the Dragon
To quote from the jacket copy of the paperback edition:
"Liz Connors can't say exactly why she's gotten herself mixed up in a search for a missing person. But when her former employer Carl DiBenedetto, head of the English Department of a Boston-area college, asks for her help, she can't say no. He's desperate for Liz to find Bonnie Nordgren, a beautiful young teacher who dropped out of sight--still toting the thirty-five hundred dollars she borrowed from Carl.
On a lark, Liz starts checking around...she cleverly follows a smoky road of deceit that leads straight to Bonnie's front door, for an illicit education that needs no advanced degree."
"Susan Kelly writes wittily and well about the Boston-Cambridge area." -- Mystery News