The REAL horror of this film is only implied. SPOILER ALERT
Almost everyone seems to think this is a sweet little Vampire romance story, with a cute couple of kids running away to live happily ever after in Never Never Land.
This movie, although it never comes right out and states it, is actually a bleakly terrifying story about a naive hopeless 12 year old boy basically selling his soul to an ancient, evil creature, getting a few decades of love and companionship in return for becoming a slave and aging into an old pedo creep who murders innocent people to feed his mistress.
About 50 years ago, The Father was just like Owen, as seen in the old photo Owen finds. He too was some lonely misfit kid seduced by Abby into running away from his family and devoting his life to serving her needs.
However, The Father aged and Abby did not. Soon, they were no longer a couple of cute kids on an adventure, but a creepy older guy obsessed with a prepubescent girl to the point of murdering for her. The situation just became sicker and bloodier and weirder until The Father finally found himself pouring acid over his head and sacrificing himself to save Abby, while she grooms his juvenile replacement right under his nose.
The same sort of fate awaits Owen 50 years down the line. He will be the creepy old man living in shitty apartments with a monster who looks like a 12 year old girl and murdering people for their blood so she can feed.
Abby has done this countless times over the centuries. What makes Owen any different from his predecessors? Any attempt to gloss this over and claim "this time is different" and Abby will turn Owen into a real vampire too and they'll be happy forever together is a cop-out and turns the story into a fluffy fantasy instead of a horror film.