Boo! Aw, having trouble? Take a seat. Have a drink. You look like a man who takes himself too seriously. Do you want my opinion? You need to lighten up.
~ Scarecrow to Batman after exposing him to the fear toxin.
Dr. Jonathan Crane, also known as Scarecrow, is a major antagonist in The Dark Knight trilogy from Christopher Nolan, serving as the secondary antagonist of Batman Begins and a minor antagonist in The Dark Knight and The Dark Knight Rises.
~ Crane, revealing his true identity to Carmine Falcone.
Dr. Jonathan Crane started off as a university professor in psychology. He took advantage of his profession by testing his "Fear Gas" on his students, driving them into insanity. He was finally exposed and fired after one of his students jumped through a window to assault a Santa Clause mannequin. Wanting to protect their reputation, the university fired him in secret. It was then that Crane started working at Arkham Asylum where he'd subject the patients to the same treatments.
In order to maintain Falcone's participation, Crane had Falcone's thugs, including Victor Zsasz, declared insane and moved into Arkham Asylum, rather than facing criminal charges, which Assistant District Attorney Rachel Dawes found highly suspicious.
Later in the film, after Falcone was captured by Batman and imprisoned in the Blackgate Penitentiary, he slit his wrists in order to get an insanity plea. When Crane was summoned to inspect him, Falcone attempted to blackmail him into letting him in on his and Ra's al Ghul's plan. Instead, Crane put on his Scarecrow Mask and gassed Falcone with his Fear Toxin, which left him in a state of psychosis and had him moved to Arkham Asylum on suicide watch.
When Rachel heard about Falcone being moved to Arkham, she was once again suspicious. She personally went down to Arkham to meet with Crane, and believed Crane himself to be the one responsible for Falcone's condition. Rachel informed Crane that she had arranged for a doctor from County General to have their own evaluation of Falcone that same night and to be on the Judge's desk by the next day. Crane took Rachel down to the basement level and showed her where his Fear Toxin was created. Frightened, Rachel attempted to escape, but Scarecrow caught up with her and gassed her with a consecrated dose of his Fear Toxin. However, before he could continue experimenting on her, Batman arrived, battled Scarecrow, and eventually gassed him with his own Fear Toxin and learned that he was working for Ra's al Ghul. Crane was eventually put in a straitjacket and imprisoned with Arkham itself.
Near the end of the film, when Ra's al Ghul's men released the Arkham Asylum inmates, Scarecrow was freed as well, and when the Fear Toxin was mass-released into the air by Ra's, he was encountered riding on a horse he stole from an officer he killed by Rachel and a young boy as a demonic looking rider. However, Scarecrow was chased away after Rachel used a taser on him. That was the last time that Scarecrow was seen in the film.
Selling his Fear Toxin
Buyer beware. I said my compound would take you places. I never said they would be places you wanted to go.
~ Scarecrow in The Dark Knight.
Scarecrow briefly appeared at the beginning of The Dark Knight, and was still on the run after being released in the previous movie. Before Batman focused on battling against the chaotic anarchist, The Joker, he learned that Scarecrow attempted to sell his Fear Toxin to The Chechen, a crime boss who operated in Gotham and was also an ally of the Joker's, but was interrupted by a group of Batman impersonators. In the novelization, he tested his Fear Gas on a junkie and murdered him before selling them as hallucinagens. Scarecrow could immediately tell that those weren't the real Batman because they had guns (something which the real Batman didn't use). Eventually, Scarecrow spotted the real Batman. In the chaos, Scarecrow attempted to escape in a van. However, the real Batman caught up to him and successfully captured him, by dropping on top of the van.
Death or exile?
In The Dark Knight Rises, Crane appeared as a minor antagonist, following Bane's launching of Gotham City into anarchy. After being set free from Blackgate Penitentiary, Dr. Crane served as a judge for mock trials against the rich and powerful of Gotham City's citizens, who usually offered the options death or exile, which both lead to the victim's deaths. Scarecrow's ultimate fate was unknown, but it was assumed that he was returned to Arkham Asylum.
In the novelization of Batman Begins, Scarecrow is well aware of the League of Shadows' plan to drive Gotham into wiping itself out in a fear-induced insanity and looks forward to using the millions of civilians as a "test" for his gas-unlike in the film where he thinks they're just going to blackmail the city for ransom.
Scarecrow was one of two main villains in the Dark Knight trilogy who didn't die, the other being the Joker.
Scarecrow was the only villain that appeared in all three of Christopher Nolan's Batman films (as well as one of five characters that appeared in every film as well, the others being Batman/Bruce Wayne, Alfred Pennyworth, Lucius Fox, and Commissioner Gordon).
He appears also in one of the short films in the short film collection Batman: Gotham Knight, which is supposed to be canon with Christopher Nolan's films. However, given the many tonal and content-based inconsistencies with Nolan's films that are in Gotham Knight, just how canon or compatible with Nolan's films Gotham Knight is is ambiguous.