The idea of the Shadowhunters (Mortal Instruments) AU is haunting me.
Just imagine Allison as Clary - her father is an ex-’hunter who ran away to keep Allison safe from her grandfather (Gerard as Valentine). However, Allison hates constantly being uprooted and moved from house to house. She and her dad settle down in a small apartment in Beacon Hills. She and her friend, Scott, (who has an unrequited crush on Allison and is secretly a werewolf who watches over Allison - so a mix of Simon and Luke) go out to an all-ages club one night because they’re holding a neon party and Allison really wanted to go.
When there, something catches her attention; a girl (Lydia) flirting with an unsuspecting young man. Something seems off so she follows them and finds them with another young girl (Cora) and two other guys (Isaac and Derek) in a supply closet, arguing and fighting. She witnesses the fight that ends with the lured guy being killed. That’s when the others seem to notice her. They’re shocked; she shouldn’t be able to see them. Scott finds her and she begs him to leave.
When she gets home, her dad is mad at her for staying out so late. Then he drops the news on her that they’re moving again, which makes Allison furious because she only just finished unpacking and she likes where they live. She runs away and stays at Scott’s ignoring her father’s persistent phone calls.
She stays up all night, the memory of the guy in the supply closet being murdered burned into her brain and her stomach churning with guilt after fighting with her dad. Unable to sleep, she sits up and goes to sit in the window and stare at the stars. Se sees a guy down on the street: the guy from the club (Isaac).
She pulls her jacket on and runs downstairs to confront him, barraging him with questions about why she can see him and no-one else, about why he and the others murdered someone in the club and why he’s following her. Isaac begins to explain a few things when Chris calls. Allison caves and answers. Her father is panicked and the noise behind him sound ominous and threatening. She runs home to find her dad missing and her house trashed.
She gets attacked by a demon and has to fight them to the death. She gets bitten and is slowly dying when Isaac comes to her rescue. He takes her to the Institute where she is cared for while she recovers.
When she gets back on her feet, she goes to meet their tutor: Deaton.
Allison desperately tries to find her father, uncovering secrets about her family, her best friend and her heritage.
Along the way they need Stiles, a super-powerful warlock who Chris used to go to when Allison remembered her past, and things between him and Derek begin to blossom.
In the end, she embraces her Shadowhunter lineage, training with Lydia, Cora and Isaac (Derek doesn’t like her much) until she becomes a badass ‘hunter.
Maybe there’s a little bit of a love triangle, but definitely not as suffocating as the canon triangle between Clary, Jace and Simon (and maybe they just end up together, all three of them, idk), and no incest scare - just her grandfather wanting to corrupt her.