We don’t believe, we only fear.

Renard calls Nick and Hank into his office and tells them that he is going to Europe to deal with the aftermath of his brother’s death. He is claiming to go to Tahiti for a vacation as a cover story, and tells them that he will only contact them through Rosalee so they shouldn’t trust any other apparent messages from him.

The Kearys bring their nine-year-old son Daniel to a church in Portland. A seminary student, Matthew Bard greets them and takes them to Monsignor Paul Dobbs, who is expecting them. The Monsignor assures Daniel that theirs is nothing to worry about and that he will try to help. Daniel’s parents reluctantly leaves them with Dobbs and Matthew, who tie Daniel to a table and bolt the door. They then begin an exorcism. Daniel sits up, snarling, and his face transforms into a demonic visage. Mr. Keary hears the sounds and runs to investigate, pounding on the door. Meanwhile, Daniel snaps the rope holding his arm to a mounting and smashes Matthew away, and then beats in Dobbs’ head with the metal stanchion.

The police get the call and Nick and Hank arrive at the scene. Lee tells them what apparently happened, and confirms that Dobbs is dead and that Matthew is being taken to the hospital. They check out the Monsignor’s office and Nick, using his enhanced hearing, notices Daniel hiding in a cabinet. The officers bring in Daniel’s parents and he runs to them for comfort.

Nick and Hank take Daniel to the hospital where Dr. Saunders tells them that Daniel is suffering from high levels of stress and an increased white blood cell count. They’re keeping Daniel sedated for the next day or two, and the detectives can talk to him then. Nick and Hank then talk to Mr. Keary, who explains that Daniel has been having vicious mood swings for the last year. He has no memory of doing anything afterward, and everyone they’ve taken the boy to has been unable to find a cure. Eventually they contacted Dobbs, who believed that Daniel was possessed by a demon. Nick, suspecting that Daniel is a Wesen, confirms that the boy is the Kearys’ biological child. Mr. Keary says that Daniel has sometimes transformed, as if there is something inside of him trying to get out. The father claims that he hasn’t made anyone else make similar transformations. As Nick and Hank leave, they consider whether one of the parents is a Wesen and has kept the knowledge from the other.

As Daniel lies in his bed, his features basically change and then go back to normal.

Meisner picks Renard up at the Vienna airport and explains the political situation with the Resistance. Renard wonders where they’re going and Meisner warns him that it’s somewhere that he won’t like.

Nick and Hank go to the spice shop to consult with Monroe and Rosalee to see what is possible under the circumstances. The Wesen manage to avoid going into too much detail about what would happen if a mixed-breed Wesen was born given their own situation, but insist that they would be fine with it as long as the child was healthy. As they talk, the detectives get a call that Matthew has woken up.

Meisner takes Renard to a cellar used by the Resistance safehouse. Renard looks around and admits that it looks similar to one that he and his mother hid in when she fled the Royals. Meisner points out a hidden tunnel leading to the Danube, and tells Renard to stay there until they receive word about the meeting.

Matthew tells Nick and Hank about the exorcism procedure and assures them that the Monsignor eliminated every other possibility before seeking permission for the exorcism. He describes the ritual and how Daniel’s face transformed into a demon before he broke loose.

A nurse goes in to check the sleeping Daniel’s vitals.

Once they’re alone, Nick and Hank discuss possible theories. Hank wonders if one parent is human and the other Wesen, but Nick figures that the Wesen parent would have said something rather than let Daniel suffer.

Daniel transforms again and snarls at the nurse. She runs out into the hallway, into Nick and Hank. Nick goes in and watches, surprised, as Daniel briefly transforms. As Hank comes in, Nick figures that the “demon” reacts to confrontation. He orders everyone to stay outside and tells Dr. Saunders not to do anything that could be perceived as a threat. She reluctantly agrees but gives Nick 24 hours to deal with the situation. After that, she will have Daniel removed for the safety of the hospital staff.

When Adalind returns to her hotel room, she gets a call from an unidentified man. He tells her to come to the house that night and that a car will be sent for her.

Back at the spice shop, Nick and Hank tells Monroe and Rosalee what happened. Monroe reluctantly suggests that they may be dealing with a Grausen, a mythical spirit said to possess human children. Rosalee admits that given modern science, many Wesen believe that it is now some kind of mutation. Because of a mutual agreement by the Grimms and the Royals, the Wesen Council deals with any Grausen appearances, since if their host grows to maturity they often become psychopaths and serial killers. Rosalee warns that all Wesen are required to report any sightings of a Grausen to the Council, and they could be executed if they don’t. Once the partners leave, Rosalee tells a reluctant Monroe that they have to contact the Council.

A short time later in Europe, the Council receives Rosalee reports and their representative De Groot sends an agent, Alexander, to America to investigate.

Nick and Juliette go through the Grimm journals and find a reference to one. The Grimm making the entry believed that the Grausen was a disease, not an evil spirit, and let the Council handle the creature. Nick remembers Dr. Saunders’ comment about Daniel’s elevated white blood cell count and they figure that Daniel was infected approximately a year ago when he first started having mood swings. Juliette figures that the boy was somehow infected and agrees to go with Nick since he doesn’t understand the medical terminology involved.

Renard wakes up when he hears someone moving upstairs. Thinking quickly, he grabs Meisner and they hide beneath the stairs as two Hundjager assassins move in. Renard and Meisner take them out and confirm that they have Verrat tattoos. As more killers move in upstairs, Renard and Meisner escape through the tunnel.

Nick and Juliette arrive at the hospital and Mr. Keary is furious that the doctor won’t let him see his son. Juliette questions the Kearys where they were a year ago and they confirm that they went with a tour group to the Middle East. Daniel swam in the river and came down with a case of the flu shortly thereafter. He recovered three days later and has been fine ever since. Back at home Juliette is clearly distracted and suggests that a parasite rather than a disease is causing Daniel’s mood swings. She tells Nick that a parasite could be responsible, and that he heard a story from a fellow vet of a pack of horses transported from the Middle East. They displayed aggressive behavior and the vet believed that a protozoa was responsible, but the horses were destroyed before they could be treated.

Monroe hears a knock at Rosalee’s door and goes to answer it. He freezes in panic when he sees that it’s Alexander. Alexander demands to know where he can find Daniel and Rosalee finally says that Daniel can be found at the hospital. The Council agent thanks her for her loyalty to their organization and leaves, and Monroe insists on calling to warn Nick despite the risks if the Council finds out.

At their house, Juliette is trying to work out a way to kill the protozoa when Monroe calls Nick and tells him that Alexander is on his way to the hospital. The Blutbad offers to go to the hospital to help identify the man, but Nick, well aware of the risks to his friends, tells him to stay where he is. As they talk, Nick receives another call.

When he gets to the hospital, Alexander enters Daniel’s room.

When Nick and Juliette arrive at the hospital, they go to Daniel’s room and discover that the boy is gone. Dr. Saunders arrives and tells them that she released Daniel to go home when she was unable to diagnose or treat his condition. Hank arrives in response to the earlier call and they go to the Keary house… unaware that Alexander is hiding in a nearby conversation, listening in.

Mr. Keary and Nancy are trying to work out what to do next when Juliette and the detectives arrive. Juliette explains that Daniel was infected with a parasite and they may have a cure. They make sure that Daniel is sleeping, while Alexander secretly watches them from the window. Once they leave, the Council agent slips into the room and transforms into a Balam, preparing to kill Daniel. However, the boy wakes up and lunges at him.

As Nick and Hank prepare an APB for Alexander, they hear the fight upstairs and run up. They arrive just in time to see both Daniel and Alexander dive out the window. Nick goes out the window after them while Hank goes downstairs and out. Alexander finally catches the running boy, but Nick arrives and attacks the Balam. As Daniel runs away, Nick manages to knock down his opponent. Hank arrives and holds Alexander at gunpoint while Nick goes after Daniel. The boy, exhausted and chilled to the bone, finally stumbles into a play fort that his father built for him and then passes out.

Mr. Keary, Nancy, and Juliette arrive and Mr. Keary leads Nick to the fort. They find Daniel, unconscious and suffering from hypothermia, and the boy starts to transform again. Nick realizes that the parasite is dependent on the body, and Juliette suggests that the parasite can only exist in a certain temperature range. The hypothermia could kill the parasite. Nick asks Mr. Keary what he wants to do. As they talk, black ooze pours out of Daniel’s mouth and nose, and Juliette has Nick take a sample of the now-dead parasite. They then take Daniel back to the house to warm him up.

When Adalind arrives at the Royal home, a man invites her in and says that he’s been looking forward to meeting her.

Meisner leads Renard to the sewers going to the Danube and explains that they have a safehouse waiting for Renard. When Meisner starts to call them, Renard throws his phone into the river and calls on his own.

At the station, Nick talks to Alexander privately and explains about the parasite and how Daniel is cured. He gives the Council agent Juliette’s medical report confirming his explanation. When Alexander objects, Nick cites the treaty, giving Grimms authority to deal with such situations as necessary. Much to Alexander’s surprise, Nick tells the agent that he’s free to go. The Grimm says that they live in an enlightened age now, one where fear doesn’t drive belief.

Later, Alexander reports to De Goot about what happened and shows him the medical report. They conclude that Nick isn’t like the other Grimms they’ve dealt with and De Groot agrees to monitor both Nick and Daniel.

At the trailer, Nick concludes his journal entry about Daniel and Juliette helps him with the medical terminology. She points out that it’s hard knowing what to believe.