Nick and Hank walk into Captain Renard's office and Renard tells them he is leaving town for a little while. He tells them to ignore any communication directly from him such as texts and emails because it won't be him. If he does need to contact them he tells them he will do it indirectly through Rosalee. Nick asks if there is anything they can do and Renard says that if anyone asks, he's having a wonderful time in Tahiti.
Daniel Keary is brought to a church by his mom and dad to have an exorcism performed by Monsignor Paul and a seminary student, Mathew Bard. Monsignor Paul tells Daniel he is going to try to help him and he isn't going to hurt him. Daniel's parents hug him and tell him they will be right outside the room. His parents leave the room and Mathew locks the door. Outside the room, Mr. Keary is pacing back and forth wondering why he or his wife can't be in the room with their son. Mrs. Keary tells him it's going to be alright and it's going to work. In the room, Daniel is laying on an altar and Monsignor Paul begins the exorcism. Daniel clenches his fists and quickly sits up. Monsignor Paul tells Mathew to hold him down to ties his hands so he won't hurt himself. Suddenly Daniel's face becomes pale, his eyes darken, and what appear to be black veins appear all over his face. Daniel's parent hear the commotion and try to go in the room, but can't because the door is locked. Daniel starts to go wild and hits Mathew, knocking him out. Daniel then breaks off a metal piece from the side of the altar and hits Monsignor Paul, causing him to go flying across the room hitting a wall, killing him.
Nick, Hank, Wu, and many other officers and medical personnel arrive at the church. Mathew is on a stretcher being loaded into an ambulance and Wu tells Nick and Hank that Monsignor Paul was killed, which disappoints Hank. They go inside the church and Wu tells them Daniel is missing. Wu points out Daniel's parents who are being interviewed by another officer. Nick, Hank, and Wu go into the room where the exorcism took place and Monsignor Paul's body is still lying on the ground. The room is a disaster site and Nick says it took a lot of force to kill Monsignor Paul. Hank says the parents were the first ones in the room and wonders if they could have something to do with what happened. Nick hears something and he turns around to open a cupboard door on the altar where Daniel is hiding. Hank goes to get Daniel's parents while Nick unties the rope from Daniel's wrist and puts it into the evidence bag Wu is holding.
Nick and Hank talk to Dr. Saunders at the hospital Daniel was taken to. Dr. Saunders tells them Daniel's immune system has been radically stressed, his platelets are down, and his white blood cell count is up. Dr. Saunders tells them more tests will be run on Daniel in 48 hours to check things out again. Nick asks when they can talk to him and Dr. Saunders tells them in 24-48 hours because he's been sedated since arrival and they need to bring him out gradually. Nick and Hank talk to Mr. Keary who tells them Daniel seemed to change overnight about a year ago. He started having wild mood swings where he became violent and abusive, and doesn't even know he's doing it. Mr. Keary says Daniel was taken to many doctors and psychiatrists but no one could diagnose him. Nick asks Mr. Keary if he has noticed a physical change with Daniel and he says that he's seen Daniel's face change like something is inside him trying to control him. Nick and Hank leave and discuss the possibility that Daniel is Wesen. Nick says that would mean one or both of the parents would also likely be Wesen and they won't be able to hide it for long if they are.
At the Vienna International Airport, Meisner picks up Captain Renard. Renard tells Meisner it's been a long time since he's been back and Meisner says that he's doing his best to not let anyone find out. Renard asks where they're staying and Meisner tells him somewhere he won't like.
Nick and Hank head to the Spice Shop to talk to Monroe and Rosalee. Nick asks Rosalee what a kid who has one human parent and one Wesen parent would be. Monroe then says it must be time for the birds and the bienen (birds and the bees) Wesen talk. Monroe says if both parents are Wesen, the kid will be also. Rosalee then says that if one parent is Wesen and the other is Kehrseite then it's a 50/50 chance the child will be Wesen. However if the parent is Kehrseite-Genträger instead then the child will be Wesen for sure. Hank then asks what would happen if the parents are two different species of Wesen and Monroe says then it's a Vorherrsch situation meaning the more "dominant" type will be what the child is, although there are health risks. Nick gets a call from the hospital saying Mathew is conscious, so he and Hank go to talk to him.
Back in Vienna, Renard and Meisner arrive at an underground safe house. Renard says the last time he was in a place like this, he and his mother were running for their lives from his family. Using a trick taught by his now deceased father, Meisner removes a step from the wood stairs to act as a trap against any trespassers and later shows Renard the second way out of the safe house which leads to the sewers.
At the hospital, Mathew tells Nick and Hank what happened. Nick asked him if they expected violence and Mathew said he tried to hold him down when "the beast fought to control him." They were concerned Daniel would injure himself. Nick asked if he saw a physical change in Daniel and Mathew said what he saw "wasn't the face of Daniel. It was the face of a demon." Nick and Hank leave the room. Nick says he doesn't think Daniel is Wesen, but he doesn't know what he is. In Daniel's room, a Nurse puts a needle in his arm to draw blood, but before she can get any, Daniel wakes up and his face changes which scares the nurse. She runs out screaming and runs into Nick and Hank, saying she saw some kind of monster in Daniel. Nick goes into the room and Daniel is sitting up in his bed with his head down. Nick checks on him, but when he lifts his head his face changes again surprising Nick. Hank comes into the room and sees Daniel. Nick asks how they are supposed to handle this and Nick says he thinks they should stay back. Daniel's face changes back to normal and he puts his head back on his pillow. Nick tells Hank he thinks what ever is going on with Daniel reacts to confrontation. Hank says he thinks they need to put a guard at the door and Nick agrees. Nick leaves the room as Dr. Saunders is going in. Nick tells her not to do anything that can be perceived as a threat. Only food and observation.
Adalind arrives at her hotel room and her phone rings. The person calling says her presence is requested later that night at the house. Adalind asks what it's about and the voice just tells her they'll send a car.
Nick and Hank go back to the spice shop and tell Monroe and Rosalee about what they just saw with Daniel. After Nick tells them Daniel didn't woge and his change was more of a battle within, they look at each other and both guess Daniel is a Grausen. Monroe and Rosalee say stories about Grausens go back centuries and people used to think it was a Wesen spirit that would invade a child. It was never a Wesen child, only humans. Rosalee says the thinking has changed since science and medicine have advanced to the point people think it may be a mutation. Rosalee says all cases are dealt with in the same way; the case is reported to the Wesen Council and the Grausen would disappear. Rosalee says if they're dealing with a Grausen case they have to inform the council and Monroe says that's a death sentence for Daniel, but Rosalee says that it's a death sentence for them if the council finds out they didn't report the case.
Alexander walks into De Groot's office and De Groot tells him that there is a report about a possession of a child. Alexander asks what they know and De Groot tells him not much, but a priest is dead and a nine year old boy is in the hospital. De Groot tells Alexander this is his mission and asks him if he accepts responsibility for what must happen, and Alexander says yes.
Nick and Juliette are at home reading one of Nick's books about Grausen. They read that there are some Grausen reports from 1683, 1741, 1804, and 1920. Each time the Grimm originally thought they were dealing with Wesen. Juliette reads that the Grimm and 1920 thought that Grausens were caused by some kind of disease and Nick tells Juliette the hospital said Daniel's white blood cell count was high and his immune system was stressed. Juliette says that sounds like an infectious disease. Nick tells her everything started a year ago and Juliette says Nick needs to talk to the parents about what happened then. Nick isn't very confident about talking to the parents about pathogens, so Juliette says she'll go with him.
Back in Vienna, Renard and Meisner are sleeping, but both wake up when they hear the floorboards above them creaking. Suddenly the door at the top of the stairs bursts open and two Hundjäger shoot their guns at Renard and Meisner's beds, although neither is in bed anymore. They both come down the stairs, but fall down when they get to the step Meisner removed. Renard and Meisner each take out a Hundjäger and they notice both of them are Verrat. They grab the Hundjäger's guns and exit to the sewers.
Nick and Juliette arrive at the hospital to talk to Daniel's parents. Mr. Keary is upset that the officer guarding Daniel's door won't let them in, but Nick says they can't take a chance of anyone else getting hurt. Nick introduces Juliette as someone helping him on the case and she asks the Keary's what happened a year ago and Mr. Keary says nothing. Juliette asks them if something happened a month or two before that and Mrs. Keary says they went on vacation in Egypt, Israel, and Jordan. She tells them Daniel got the flu on the vacation and was sick for a few days, but then he was fine. Mr. Keary asks when they can see Daniel and Nick says he'll check.
Back at their house, Juliette tells Nick she doesn't think Daniel's behavior is caused by anything viral or bacterial. Juliette tells him a colleague of hers from vet school did a case study about a group of thoroughbreds flown to Dubai for a race, but they had to land in Jordan because of a storm. By the time they got back to the US they exhibited aggressive behavior. The colleague discovered the horses behavior was caused by a protozoa similar to Toxoplasmosis and if the parasites could be killed from within the horse's behavior would return to normal. Nick asks her if it worked, but Juliette says the horses were killed before any treatments could be done.
Monroe comes down his stairs in the middle of the night because someone is banging on his door. He thinks it is probably Nick and says to himself "this is really pushing it Nick." When he opens the door he is surprised it isn't Nick. It's Alexander who says he is looking for Rosalee and that it's Council business. Rosalee comes down the stairs and Alexander asks where the boy is. Rosalee pauses for a second, but reluctantly tells Alexander that Daniel is at the hospital. Once Alexander leaves, Monroe locks the door and tells Rosalee he has to tell Nick. Nick and Juliette are lying in bed talking about how they could kill the protozoa inside Daniel when Monroe calls. Monroe says they didn't have a choice so they had to tell Alexander where Daniel was. Monroe says he wants to go with Nick to the hospital because he can identify him, but Nick says no because it could jeopardize him and Rosalee.
Alexander arrives at the hospital and walks into Daniel's room. The curtains are closed around the bed and Alexander opens them. Nick and Juliette arrive at the hospital and go to Daniel's room. When they arrive, they only see an empty bed. Dr. Saunders comes into the room and tells them they released Daniel half an hour ago because they don't know what to treat him for. She tells them Daniel's parents took him home and the hospital needs beds for people they can treat. Hank arrives at the room and Nick says they need to get to Daniel's house. As they leave, Alexander appears from inside a closet in Daniel's room.
At Daniel's house, his parents are talking about him. Mrs. Keary says she doesn't feel safe and doesn't know what to do. Mr. Keary asks what they can do since Daniel is their son and Mrs. Keary asks him what if Daniel does to him what he did to Monsignor Paul. There's a knock at the door and it's Nick, Hank, and Juliette. Juliette tells them they think they know what's wrong with Daniel. She says that he may have become infected with a rare protozoa when he was swimming on their vacation and his flu may have been more than just a flu. They go up to Daniel's room to check on him, but he is sleeping so they leave. As they leave, Alexander looks in through a bedroom window. Alexander comes into the room, stands over Daniel's bed and woges into a Pflichttreue. Daniel wakes up, his Grausen side comes out and he punches Alexander. Everyone hears a crash inside Daniel's room and Nick and Hank quickly check it out. As they open the door they see Alexander dive out the window and Daniel is no longer in his room. Nick goes out the window to go and find them. Daniel is running through the woods in the rain and trips. He falls into a big puddle which soaks him. He pauses, but gets up and starts running again. Alexander jumps out at Daniel, but Daniel ducks under him and Nick catches up, so he tackles Alexander while Daniel runs off. After a brief fight, Nick knocks Alexander against a tree. Hank runs up and tells Nick he'll handle Alexander while Nick goes after Daniel. Daniel starts getting tired and stumbles into a little fort where he lays down and closes his eyes, freezing. Nick continues looking and runs into Juliette and Mr. Keary. Mr. Keary says he think he knows where Daniel went and leads Nick and Juliette to the fort he and Daniel made together. Juliette tells Nick it's really cold and if Daniel is out there much longer he could die. They arrive to the fort and find Daniel passed out. Juliette says he is really cold and he is probably hypothermic. Juliette says they need to get him back to the house but Nick says the thing in Daniel is dependent on body temperature and asks what could happen if the body was too cold for it. Juliette says it would kill the parasite, but Mr. Keary asks how they know Daniel won't die too. Juliette says they can't take the risk, but Nick says this could be his only chance and tells Mr. Keary it's his decision. Before he can decide, the parasites start coming out Daniel's nose and ears where they die. Juliette tells Nick to get a sample and they rush Daniel to the house where they warm him up.
In Vienna, Adalind arrives at the castle. She waits around for a bit before a man comes and tells her the prince will see her now. Adalind is confused about him talking about a prince and he tells her life goes on and so does the family business. The man opens the door and a voice says, "Hello Ms. Schade. I've been looking forward to meeting you."
Elsewhere in Vienna, Renard and Meisner arrive in the sewers. Meisner says they need to get out of there and pulls out a phone. Renard grabs it from him and throws it away. He then pulls out his phone and says, "my turn."
Nick goes to the interrogation room where Alexander is waiting and drops a folder in front of him, telling him it's Daniel's medical reports. Alexander asks him what it proves and Nick tells him Daniel was infected with a parasite that caused him to be what the council called a Grausen. Nick tells him "it's not possession by demon, it's not a mutation, and Daniel has been cured." Alexander tells Nick he should know better since he's a Grimm and that he needs to see Daniel. Nick says he needs to take his word for it because of what his ancestors and the council agreed to in the Charter of Wittenberg in 1682. Nick tells him to take the report with him when he leaves, so the council can read it. Alexander is surprised Nick is letting him go and Nick says, "I like to think we live in an enlightened age where fear does not drive belief. That's the truth behind the fear."
Alexander takes the report back to De Groot who asks him if they believe the report. Alexander tells him Nick didn't have to let him go. De Groot says some of the things they've heard about Nick must be true and Alexander says he's not like anything they've ever dealt with. De Groot says to monitor Daniel and Nick.
Nick and Juliette are in the trailer and Nick is writing a new entry on Grausens regarding Daniel's case in one of the books. Nick says that the parasite could no longer survive when Daniel slipped into hypothermia. He also writes that a parasite known as Daemoni adspicio was responsible for the behavioral changes in Daniel.
A YOUNG BOY’S AILMENTS LEAD EVERYONE TO THINK THEY ARE DEALING WITH A CASE OF DEMON POSSESSION – Nick (David Giuntoli) faces his toughest challenge yet when he and Hank (Russell Hornsby) investigate a case that combines religious phenomenon with the dark dealings of the Wesen Council. Meanwhile, Rosalee (Bree Turner) is torn when Nick’s case challenges her Wesen loyalties. Elsewhere, Captain Renard (Sasha Roiz) leaves town to tend to some “family matters.” Bitsie Tulloch, Silas Weir Mitchell, Reggie Lee and Claire Coffee also star.
- Filming for the episode began on September 10, 2013.