First of all, I wasn't fooled for a moment by the plot's suggestion that the caller and the woman living alone were supposedly strangers to each other. Their eye contact and body language gave them away, not to mention Malcom McDowell's immediate, overconfident attitude the moment Madolyn Smith Osborne first opened the door to him and how too gullibly she believed his story about his car breaking down. She didn't seem the least bit nervous as one would normally expect her to be.
The old, familiar movie plot of a stranger asking to come into someone's home to use their phone has been done so often you'd think people would have wised up by now, based on the horrific reality of well-publicized home invasions.
Why can't the homeowner simply say, "Just wait outside and I'll call the police (or towing company) for you."? Then make sure you lock the door!
Personally, if I ever needed to get help, I'd simply shout out to anyone within range, "Please call 9-1-1! It's an emergency!". No need for me to request entry into someone else's house, thereby giving them a reason to suspect any ulterior motive on my part. That being said, if someone offers to help me in other ways, that's perfectly fine, but that's THEIR call.
Regarding The Caller's plot: as the truly unlikely and increasingly bizarre dialog between the two "strangers" developed, I began to think that the REAL story might turn out to be either
(1) McDowell, was actually a director employing a rough, "hands on" test of hopeful actress Osborne for a film he was casting, or
(2) about an actual married couple engaging in a game of role-play whereby they pretend they don't know each other but want to have a bit of fun, so to speak, to relieve boredom.
There is a particular movie (the name of which escapes me for the moment) that I had once seen where the lovely Carol Lynley opens her door to a "salesman" who, however, she's well-aware is her boyfriend, after which she lets him in and the "so, what can I do for you?" game progresses or deteriorates accordingly.
I must admit, though, that the sci-fi ending to The Caller surprised me. Perhaps the writer and producer ran out of ideas and decided to toss this one at us like a hand grenade?
Tingnan pa 
