Carolyn Wells 
Mystery Girl 

John Waring seems to have everything to look forward to. He’s just been elected as president of Corinth University, and his engagement has been confirmed to an attractive local widow, who loves him dearly. But then there appears on the scene a beautiful and mysterious young woman who’s quite clearly lying about who she is. At sight of her, Waring is clearly more than startled. Later that night he continues to work alone in his study, all doors locked, and the following morning he’s found dead at his desk, stabbed in the jugular. Aside from the locked doors, just to make matters more mysterious there’s no trace of the weapon. There are, however, small footprints in the snow outside the study’s French windows, and these lead toward the boarding house where the Mystery Girl is lodging. (goodreads)