The movie itself opens up after the death of Emily Rose, on a farmstead much like any small farm in countrysides across the continent. However, this is not the setting, or even a major point of the film; our view is set on the courtroom, where Father Richard Moore is set to be tried for the neglectful homicide of Emily Rose.

Erin Bruner, an up and coming junior partner, having just released a man charged with serial murders from prison, is brought to represent the priest against a prosecutor whose own faith and convictions lead him to believe that Emily was murdered. His case involves medical testimony and the belief that Emily simply suffered from epilepsy, which is later revealed to have brought about psychosis.

As the movie progresses, strange and unexplainable events occur to Erin herself; she wakes up in the middle of the night, alarm clock stopped at 3:00 A.M.

Perhaps the strangest of these is during the trial itself, after a particularly fierce failure by the defense to puncture the prosecution's case, Erin finds a gold locket laid in the snow. It had seemingly been there for hours, and was almost buried under the snow. It bore the initials E.C.B.; her middle name is Christine.

At this point, she attempts to validate the possession of Emily, whether by demons or some other disembodied spirit, through the priest's own testimony, as well as that of a psychiatrist. Most notable is her use of an anthropologist, Sadir Adani, who believes that possession is simply a basic human experience, proven scientifically by the millions who experience it every year world-wide. Unfortunately, after the accidental death of the psychiatrist, Erin's case falters, and ultimately fails; Father Moore is convicted, but is given a sentence of time served.

The leading roles in this film are filled by Laura Linney, Tom Wilkinson, Campbell Scott, and Jennifer Carpenter; Erin Bruner, Father Moore, Ethan Thomas, and Emily Rose successively. Each character plays a pivotal role throughout the film, and their own journey, particularly that of Erin Bruner, are crucial to the development of the plot.

The actors portray their given characters in masterful form, developing the belief, or disbelief in the supernatural. The musical score, while not overtly impressive, gives an eerie, almost realistic viewpoint from which the audience can step into the film, and follow the trial as if they were sitting in the courtroom themselves, hearing the events told through musical interpretation.

While synthesized, the opening sequence, inter laden with the screams and frightful noises from the exorcism itself, gives off the mood necessary for the trial scenes to continue unabashed. Scenes involving the prepossessed Emily are scored with what can be described as angelic choirs, while those involving demonic possession or simply apparitions of malicious forces are suspenseful, if not altogether strange.

However, this is not meant to confuse, or excite the audience in an overt way. The main focus of the story, while masked by trial procedure and flashback sequences, is the journey of discovery made by Erin Bruner. The reality we are given is hers; how she perceives the trial, and the events that unfolded beforehand, as well as those that unfold up until the verdict is given.

Her ideals, as placed by Father Moore, make her an agnostic, with the quote “If you aren't sure, then you are one.” She's faced with a hard-nosed protestant prosecutor, who worries more about making sure lawbreakers are behind bars, than about the forgiveness and compassion taught by his own religion.

This is beyond the expert witnesses he puts forth which seem more interested in their own agenda and medicating patients for the sake of medicating patients than finding out what's truly wrong with them. While it's for certain that Ethan, the prosecutor, isn't going to change his mind about belief, nor will Father Moore lose his convictions of faith, it quickly becomes clear that Erin is the target of spiritual change. Her beliefs can go either way, due to the unhappiness and loneliness she's come across in her ambitious drive to the top of the food chain.

To top it off, the viewers themselves are given a taste of her inner struggle as the various opinions over the true dilemma of Emily is shown visually to us, displaying both the scenarios as if she were possessed, or simply ill.

Erin grows to believe, throughout the course of the movie, that something truly is amiss. She has trouble sleeping at night, because of the strange occurrences she experiences. She becomes an at-risk character before the trial even begins, with entities seemingly invading her home, playing with her emotions by waking her up at exactly 3:00 A.M., opening a locked front door, and even playing the tape recorder on which Emily's exorcism is recorded.

It seems as though there's no hope at all for the trial, and then she tells Father Moore of the locket she came across. She asks him “What are the chances that I, of all people, would find this locket?” and that it made her feel as though she was on the right path, right where she needed to be at this moment.

It's at this point the change is visible; whereas before, she was simply not sure, Erin now believes that she's doing the right thing. Whether or not the Archdiocese wanted Father Moore to testify, Erin knew that she had to help him no matter what the price.

Before this night, however, she'd run into Dr. Cartwright, who had offered to testify as an eyewitness to the exorcism. He seemed spooked, frightened, and altogether wary about even being involved anymore, and yet came forth to tell us, the audience, as well as Erin, that Emily's condition scared him. He was holding onto the tape recorder, and was also under attack by the forces surrounding the trial.

As for the events throughout the film that only we, the audience see, and the jury only hear, or hear about, there are many. The first time Emily comes into contact with the demons who have supposedly possessed her, the experience can very easily be mislabeled as an “Old Hag” experience. She wakes up, with the smell of something burning. She checks outside, afraid something might be on fire, but instead sees a door slamming open and shut with the storm. However, when she reenters her room, she feels an invisible presence slam the door behind her, and she quickly climbs back into bed.

Then, the pencil holder on her desk rattles, and slowly moves itself off, flying onto the floor. At this point, she feels the invisible presence again, on top of her, pressing down on her chest, holding her arms. The imagery is almost that of being raped, as he the presence attempts repeatedly to pull her nightgown up, in an attempt to invade her.

With a scream, the presence is gone, and she runs wildly, to a pay phone outside. As a continuation of this experience, we find Emily in the hospital, tranquilized slightly, and already on the drug Gambutrol. At this point, another attack incurs, throwing Emily to the floor, and ultimately invading her body.

The reverse of this, however, is given as two doctors testify on the stand. When one of their theories about simple epilepsy, with visual cues for our minds, fails with the efforts of Erin, a second doctor is brought in to give an explanation for a disease known as psychotic epileptic disorder. This does, in fact, seem as though it's an appropriate possible explanation for what happened with Emily.

At this point, to those who know the true story of Anneliese Michel, it becomes very obvious that the parallels between the two stories are written intricately into the movie. While Anneliese never suffered from psychotic epileptic disorder, it was implied throughout her trial that her family and the priests induced her psychosis, bringing her into the state of "possessed" on their own.

It was said that these psychotic tendencies were brought on with help by her epilepsy, which is originally the thought that even her family had in regards to her. It was hidden so that she could go to university, and there is no account in regards to the theory given to the courts as to how or why her symptoms progressively worsened while she was away from her family and priests.

This movie, while an attempt to entertain, is also an attempt to educate. For those who take such things with a grain of salt, perhaps it was simply an entertainment feature made by Hollywood.

However, the existentialism behind the film is that of possibilities. What if this could really happen? What if God really exists? Even if God doesn't exist, what if spirits and demonic forces do exist, and we deal with them on a daily basis? The true nature of the film is implied in Dr. Sadir Adani's theory given through the course of the film: that possession is, scientifically, a basic human experience that occurs worldwide, whether or not it is verifiable or malicious in its very nature.