The Harry Potter fan community is a wonderful, slightly terrifying thing. It has devoted hundreds of thousands of words to fanfiction to fill in the gaps of the world JK Rowling created, in some cases doing a better job than official spinoffs like The Cursed Child (notoriously terrible exceptions notwithstanding).

Potter fans care deeply about their world. So it’s perhaps not surprising that a group of devoted Italian fans crowdfunded €15,000 to make a 52 minute-long film on Voldemort’s origin story.

It’s also not surprising, given the scale of the fandom, that the film, titled Voldemort: Origins of the Heir, has been watched more than 7m times since its free release on YouTube on 13 January. Warner Brothers dropped copyright proceedings against the director, Gianmaria Pezzato, and his co-creator, Stefano Presita, after they promised not to profit from the film.

What is surprising is that it’s actually … good?

Well “good” might be going too far, but expectations were low. Pezzato does weird things with camera angles, including multiple extended close-ups on the characters’ eyes; the dialogue is fairly rubbish except for one excellent scene which is lifted beat for beat from the books; and the English dubbing is not great.

But the visual effects are, in many places, better than the multimillion-dollar Warner Brothers movies. The costuming and sets are also good.

Stefano Rossi as Tom Marvolo Riddle, the Hogwarts student who later became Voldemort through the magic of anagrams, is appropriately handsome and has a way of speaking when angry that makes it look as though he is trying to unhinge his jaw – perfect for the heir of Slytherin.

As the resident Harry Potter nerd at Guardian Australia, I was given (read: begged for) the task of watching the film for review and comedy purposes. This was a good decision, because I’m not sure anyone but a devoted Harry Potter nerd could follow the plot.

There are horcruxes (objects enchanted to contain a piece of a person’s soul to ensure their immortality); continuous references to the four founding members of Hogwarts; frequent shots of Tom Riddle’s diary (the main plot point of Harry Potter and the Chamber of Secrets and the first known Voldemort horcrux).

There is also an interrogation scene in a Soviet bunker. That is not canon, unless I missed a Rowling tweet.

The basic plot is that Riddle at Hogwarts was part of an exclusive gang of four composed of the descendants of all the Hogwarts founders. Lazurus Smith is the heir to Hufflepuff, Wiglaf Sigurdsson is the heir to Ravenclaw, Grisha McLaggen (connection to odious canon quidditch bro Cormac McLggen unknown) is the heir to Gryffindor.

The heirs have a superiority complex and a fairly cheesy oath about making the world a better place. They are all looking for the heirlooms of their houses.

Riddle ruins it all by clapping sarcastically at their oath and breaking the Hufflepuff heir’s arm. Classic Voldemort.

The movie mainly follows Grisha as she tries to break into the Soviet Ministry of Magic to steal Tom Riddle’s diary in order to figure out how to “save Tom from himself”.

She is captured and interrogated by a Russian general who provides exposition and prompts Grisha to throw to a series of flashbacks in which her 12-year-old self is played by an actor clearly in her early 20s.

There is a twist at the end which is genuinely enjoyable if you don’t allow logic or the rules about how magic is supposed to operate in this universe get in the way.

Voldemort: Origins of the Heir has an average star rating of 4.7/5 on Facebook from 4,800 reviews, with points taken off for the poor quality dubbing and liberties taken with canon details of the history – a fanfiction sin some cannot abide. IMDb, meanwhile, was less kind, with an average rating of 5.8/10.

On Tumblr, where fanfiction evolved to develop entirely new species, viewers were mostly positive, aside from legitimate complaints including what fool would deliver veritaserum (truth potion) intravenously when you can just drink the stuff, and “not enough Bellatrix”. The film has already spawned its own fan art.

I wouldn’t watch it before you have seen A Very Potter Musical and certainly not before Potter Puppet Pals, but there are worse ways to spend 52 minutes – like reading My Immortal.