There aren't that many Iranian films around, so I will see any that come my way.
From early in the film, it was clear that it wasn't about the usual Iranian social issues. Firstly, there was this cult of men called neophytes (the name suits their appearance) who are subjected to the usual fear, sleep-deprivation, and pain to ensure they continue to follow the Master. The Master is your stereotypical cult leader.
The cult lives in the poorest (oh God, let it be the poorest) area of the city of Mashad, in relatively salubrious and warm surroundings. Outside of the flickering firelight of the vaulted building which houses the cult, a seemingly endless number of starving prostitutes and their children beg and freeze and try to keep clear of the serial killer who is killing several prostitutes a day.
I could not get used to the filth, poverty and suffering depicted. In fact, it still disturbs me.
After the night-time dancing of the neophytes, a man and his belongings get off a bus. At this point, I was wondering if I was going to be able to follow it. Then I quickly realised that the man had come to town to solve the serial murders. (At least, I think that's what happened. Please don't anyone burst my bubble.) From this point on, the film is a standard murder mystery (albeit an Iranian murder mystery). Yes, the cult continues to feature, but don't they so often in a murder mystery? Some very unremarkable things happen, particularly around the police investigator, and you might predict the ending. In other ways, the film gets more and more bizarre.
When the credits revealed that it was based on a true story, that explained everything. For me, when something is stranger than fiction, that's because it usually isn't fiction. It really was a strange film, and I'm glad it was made.