He's watching her every move...

Darcy was just trying to be friendly to the new boy in the office. But it's gone horribly wrong. At first it was just unwanted invitations but now Joe is sending her abusive emails, calling her late at night, unwilling to take no for an answer.
And every step Darcy takes to distance herself from him is just adding fuel to Joe's obsession. And now he knows where she lives...