some unexpected plot twists are not good

Sometimes fanfic is really weird. See, I've been reading an X-Files story, which started normal enough. It was a Profiler!Mulder story with an X-Files twist in that Mulder forms some sort of psychic connection with the killers and victims, and so on, cue to Mulderangst. Which was the kind of story I wanted to read. Only then suddenly out of nowhere some green, winged horse shows up and brings Mulder to a blue anthropomorphic cat shapeshifter alien who starts talking about fighting interdimensional demons. What? Just, what? I have no idea how this continued, because the story rather lost me at that point.

What irks me most is was that I read over half of this long novel, which I thought was one thing, and then without warning it turned into something completely different. It had a summary and warnings for all kinds of things which indicated that this was a serial killer story with child molestation, but nothing mentioned mystical furry aliens fighting evil on psychic planes. Gah. What a waste of time.