The film follows Clary Fray, who is seemingly an ordinary teenager living in New York. However when her mother gets kidnapped, she discovers that she is actually one of the Shadowhunters, a race of Nephilim who fight against demons.
A sequel based on the second book in the series was initially planned, but got scrapped after the first movie failed at the box office.
The movie contains examples of:
- Adaptation Dye-Job:
- In the books both Clary Fray and her mother, Jocelyn, have green eyes, but in the film they are brown. Their hair is also more of an auburn tone than what was described in the books.
- Jace Wayland has golden eyes in the book, but blue eyes here.
- Simon Lewis has brown eyes in the book, but has green eyes here.
- The Lightwood siblings went from having black hair in the books, to being brunettes here. Also Isabelles eyes went from dark brown to blue.
- Luke Garroway has blue eyes in the books and brown eyes here.
- Emile Pangborn has grey hair in the books and black hair here.
- Samuel Blackwell is a redhead in the books but black-haired here.
- Valentine Morgenstern has white-blond hair and black eyes in the books. Here he has dark brown hair and blue eyes.
- Adaptation Induced Plothole: In the book Simon was abducted by vampires because he'd been turned into a rat, and they mistook him for one of them. In the movie, they took him as a hostage because they wanted the Mortal Cup. The movie failed to give us any possible use Vampires could have for the Cup.
- Alternative Foreign Theme Song: SCANDAL's "Rainy" is the theme song for the Japanese release of the film.
- Ambiguous Ending: Because of the cancelled sequel, the movie ends with no one knowing for sure where Valentine is, whether Clary and Jace agree that they're not really siblings, when Jocelyn will wake up, or what will happen with the two other Mortal Instruments. But hey, at least they got the Cup.
- Beethoven Was an Alien Spy: Johann Sebastian Bach is stated to have been a Shadowhunter and wrote chords that repel demons into his music.
- Black Dude Dies First: Madame Dorothea, played by CCH Pounder, is the first named character to kick the bucket courtesy of Demonic Possession.
- Bombproof Appliance: Clary hides in a fridge with the door closed over while a cooker explodes right next to the fridge.
- Cast Full of Pretty Boys: The film has a ludicrously attractive array of males◊ in the cast - the females are pretty too, but there's much fewer of them.
- Extended Disarming: Madame Dorothea refuses to let Shadowhunter Jace inside her apartment armed. He drops his sword in her umbrella stand, followed by a knife. Then another sword, another knife, more knives... and still more knives. When he's "finished" and starts walking towards the door, she raises her eyebrows, points to his boot, and he removes one more large knife to add to the collection.
- Film of the Book
- Held Gaze: Magnus and Alec have one when they first meet. Cue the squeals of fangirls everywhere."Him. The one with the blue eyes."
- Clary and Jace also share one of these when Clary accidentally falls on top of him.
- Hollywood Nerd: Clary's best friend Simon is a shy, awkward, D&D-loving nerd who can't get her to notice that he's in love with her (and is eventually rejected in favor of the dashing hero Jace.) He is played by the gorgeous Robert Sheehan.
- Hollywood Old: 36-year-old Luke Garroway is played by 29-year-old Aidan Turner.
- In the Hood:
- Jace dons a few hoods while investigating Clary.
- Magnus Bane wears a hooded long coat when he sneaks in the Institute to heal a mortally injured Alec Lightwood.
- I Take Offense to That Last One!: Simon confronts Clary about her decision to associate with Jace when Jace steps out of the room:Simon: *whispering* Your mom is gone, and you're hanging out with some dyed-blond-wanna-be-goth-wierdo?...Jace: *re-entering room with a phone* You need to check this. Oh, and for the record, my hair is naturally blond.
- Mustache Vandalism: Plus some horns, to a photo of Jace. Somebody was really jealous...