Man with two faces

the long version

As an act of kindness, to help out her friend Barbara, Rebecca had agreed to work part-time in Barbara's secretarial bureau. But unfortunately for Rebecca, it was a gesture that misfired, since it led to her meeting with the maddening Janus Leon. He was a stern, not to say unreasonable, taskmaster, for a start. But, like the Roman god after who he was named, Janus had two faces -- and the other was that of a heartless playboy. Would he turn that face to Rebecca -- and could she survive if he did? (goodreads.com)