Ed and Lorraine Warren testified for Arne as they were convinced about the demonic possession and gave all their evidence in terms of captured camera images and videos.
However, since such c movies could never have a legal basis, the accused was convicted and sentenced to 15-20 years of imprisonment; but he got out of jail in five years due to his exemplary behavior and that he married his girlfriend while still in jail. Dry court proceedings can never be an apt subject for a suspense-horror flick and therefore, a thrilling storyline and a script was built around the case.
The film opens with the scariest scene of the movie and perhaps one of the scariest scenes ever in horror cinema history. The scene depicts the exorcism of a little boy, maybe around 10 years of age, named David Glatzel with the presence of the stricken family, Ed and Lorraine and the exorcist. The chaotically horrifying developments that follow had better be watched than explained, with the results that Ed gets hurt and has a heart attack while the character of Arne Johnson (played by Ruairi O'Connor), boyfriend of David's elder sister Debbie Glatzel (played by Sarah Catherine), looks into the eyes of the violent David and invites the demon to leave David and possess him, which, incredibly enough, happens. To my experience of horror films this is a new twist as it raises some questions: it seems to make the role of the exorcists rather dubious and that a demon or a ghost supposedly possesses someone with a definite purpose and so, why should it leave its prized victim! Anyway, this was necessary as a prologue for the reel-life Arne Johnson to go on to murder someone and face trial.
As compared to the earlier absolutely absorbing and tension-filled two films of the trilogy the third one lacks a flow of storytelling which is hampered by flashbacks, jerk-cuts and scenes left half-treated, jumping to other scenes and then coming back to the former. This can be interpreted as the stylistic treatment of the director, but it does not help storytelling keeping in mind the viewers' continued involvement. For example, Ed Warren who suffered a heart attack probably rested for about a month (not clearly indicated) during which the demon in Arne preferred to do nothing atrocious. However, the moment Ed recovers with a telepathic dream he communicates to Lorraine to warn the police about an impending tragedy in the house of Arne's employer and landlord. And inevitably, Arne in a sudden burst of possessive fit murders the landlord and is arrested by the police.
Now comes the real turning point of the story: Lorraine, with her super intuitive and psychic powers visualizes a grim connection of the Arne's act with the murder and suicide of two young girls in the recent days. The police were yet to find the body of second girl who supposedly killed her friend in a fit of the same kind of demonic possession and then committed suicide. So, for the first time in the history of the trilogy the police join the investigations with the paranormal help of Ed and Lorraine, ultimately finding the submerged body of the second girl as Lorraine leads them through a dramatically crafted and a light-n-shadow scene, eminently worth watching.