THE CABINET OF DR. CALIGARIFrancis (Friedrich Feher) and an older man are sitting in a garden, telling stories. A girl (Lil Dagover) walks past, unresponsive, as in a daze. Francis says she is his fiancée Jane and that the story of how she got that way will be amazing.It all started when a carnival came to his hometown of Hostenwall . . . (we go into flashback) . . .Francis and his best friend Alan (Hans Heinrich von Twardowski) together with Jane go to the carnival for fun. They are enticed by an older mountebank (Werner Krauss) calling himself Dr. Caligari to enter his tent to see his amazing somnambulist Cesare (Conrad Veidt) who has been asleep for 25 years and, under Dr. Caligari's command, is about to awaken.After some people enter the tent and sit down, Dr. Caligari opens a vertical cabinet shaped like a mummys sarcophagus, and we see Cesare is a gaunt young man who wakes and steps forward in extreme slow motion. Supposedly he spends his life sleeping in the cabinet and is able to predict the future when awake. Caligari brags that Cesare can answer any question whatsoever.When Alan asks Cesare how long he has to live, the answer is that Alan will die before dawn tomorrow. This unsettling prediction cuts their fun short, so Alan, Francis, and Jane go home. Jane is particularly affected, since, at that time, she was Alans girl friend although she knew that Francis was also in love with her.After night comes, we see, inside Alan's rooms, the shadows of Alan and his killer fighting on his bedroom wall.Alan is found murdered the next morning. Francis goes to tell the police after he realizes the somnambulist's prophecy has come true. Suspicion turns to the eerie somnambulist and his strange handler.Before police do anything, an attempted murder of an old woman takes place, throwing the town into panic.Back at Dr. Caligari's wagon, we see him feeding gruel to Cesare as he sits in a coffin. When police knock at the wagon asking questions, they are shown Cesare inside the coffin, and Caligari protests that he doesnt ever leave the coffin without his permission.At some point a common criminal confesses to the attempted murder of the old lady, so the police are back to investigating Alans murder only. Francis, along with Jane, keep investigating Caligari and Cesare.Caligari orders Cesare to kill Jane. Cesare creeps into Jane's bedroom and as he lifts a knife to kill her, she screams and faints. He carries Jane out of her house, leading the townsfolk on a lengthy chase. Cesare falls from a height to his death to end the pursuit.The townsfolk discover a dummy in Cesare's cabinet, and that Caligari has fled.Francis goes to a nearby insane asylum to inquire whether the fled Dr. Caligari might be a patient there. The worker he speaks with tells him he must go see the director of the institute for patient information, as he's not allowed to discuss any of that.Francis goes to the director's office and it turns out the director and Dr. Caligari are one and the same person.Francis gets the police over there and after looking through books and notebooks in the office, they discover a historical book about a mythical Caligari, who did just what Dr. Caligari is doing now, back in 1793 in northern Italy. The XIth century Caligari used a hypnotized somnambulist to murder people. The director has notes to suggest he is trying to recreate the XIth Century events.When the director arrives, after being confronted with the dead Cesare, he goes nuts, saying he must become the new Caligari, so staff in the institute put him in a straight jacket. His mania is manifest, and he is confined in his own asylum.At this point the flashback is over. The expressionist look of buildings is gone. Francis and the man who was told the story wander back from the garden to the institute patio. Cesare is standing in the corner and Francis warns the older man not to accept one of his prophecies, for he would surely die.Jane is there also, and when Francis asks her to marry him, she says she cannot marry someone not of royal blood.Then down the stairs comes Dr. Caligari (the director), and Francis quickly gets in a scuffle with him. Francis is grabbed by the staff and taken upstairs.Dr. Caligari comes to the conclusion that Francis is a maniac and that his mania is caused by his delusion that Dr. Caligari is in fact the mythic Caligari who would wander from town to town with Cesare killing townsfolk.The twist ending reveals that all of the flashback is actually Francis delusion, symbolized in the film by the distorted buildings and landscapes. Francis, Jane and Cesare are all inmates of the insane asylum, and the man he calls Caligari is the asylum director. The director, after this revelation of the sources of his patient's delusion, says that now he should be able to cure Francis.
Output: Question: What do Francis and the police investigate?, Answer: alan's murder