That actually happened to my mom. But the woman actually barged in tears, and told my mom that her boyfriend was chasing after her with a baseball bat. My mom put her on the couch and looked out the window, and he actually was!
A friend of mine just had a situation like that..He was actually the neighbor of that girl who was raped. He wasn't able to help her coz of the fact that he didnt wanna get involved and the rapist might as well just kill him if he does. that's what he was thinking.
but if things like that really happen to me i'd call the police immidiately. i think that's safer.
I'd press the police button on the alarm panel, wake up my lover and get the fire bat out from under his pillow before opening the door. I'd rather risk a strangers life in the five seconds it would take for me to do that then to just open the door and have it be a trick.