Mirror, Mirror by Dalziel Laing

Inspector Georgina Borg's life is a rollercoaster. At work, she's in charge of a case pursuing a serial killer who's remained a mystery for ten long years. She's followed his distinctive but maddeningly elusive trail from Sydney to Melbourne.

Now suddenly the killer targets a victim with an entirely new profile. Despite the change in modus operandi, Borg is certain it's the same killer.

Just when she thinks she's close to solving the puzzle and revealing his identity at last, her would-be fiance becomes the prime suspect!