Renard informs Nick and Hank that he’s going on a “vacation” to Europe.

Danny, a little boy suffering from a Wesen affliction, or something else, is brought to a church to have his demon exorcised from his body. Danny attacks the priest, killing him, and the seminary student. Nick finds Danny underneath the exorcism table and brings him to the hospital.

Nick and Hank question the father about whether Danny has any physical changes during his mood swings. Nick and Hank wonder if he’s Wesen, and if both parents, or a least one, have passed it along.

Renard arrives in Vienna, and hides out with an ally of his until his meeting. Adalind is invited to the house for dinner. Renard and his friend are attacked by

At the spice shop, Monroe and Rosalee break down the genetics of Wesen: if both parents are Wesen, then so is the child; if one of the parents is Wesen, then it’s a 50/50 shot; if the parents are different Wesen, then it’s a hybrid.

Nick and Hank question the seminary student. He describes Daniel’s face changing into the face of a demon. Nick begins to think that Danny is one part demon since the parents would not put him through an exorcism otherwise.

Nick and Hand explain the situation to Rosalee and Monroe. They wonder if Danny is a myth. Rosalee explains that every generation worries that a Wesen spirit will possess someone. It used to only happen to adults, but as medicine and science advanced some believe it happens in children. In the 1600s, the Wesen council forged an alliance with the Grimms and the Royals to make these people disappear.

Rosalee is insistent on telling the council, and the council leader informs a subordinate of what needs to be done. Later that night, Nick and Juliette go through the Grimm records of Grausen, and one of the Grimm’s believes that it’s not a possession but a disease of some kind.

Juliette wonders if he’s been exposed to an exotic pathogen, and after question the parents again they find out that he got the flu in Egypt on vacation a year prior. The council subordinate comes knocking and Rosalee, fearing Wesen law, tells him where to find him.

Daniel is released by the hospital and back home, and the councilman follows him. Nick gives chase and tackles the councilman, and leaves Hank to keep watch. Nick and Juliette find Daniel in his fort, and they wonder if his body temperature is brought down low enough then the protozoa will die. Before they can debate it any longer the protozoa escapes from his body and dies.

In Vienna, Adalind meets a mystery man.

Nick lets the councilman go, so long as he takes the report about the “Grausen” to the council. The councilman does so, and his boss asks him to monitor Nick, who is living up to the rumors that he’s unlike anything they’ve dealt with before, and Daniel.