An underground traveling carnival has set up temporary residence on the outskirts of Portland. The carnival contains a freak show featuring Wesen performers woging for unwitting audience members, who interpret the transformations as clever magic tricks.
After a show, the carnival's Blutbad performer, Max, shows signs of an ailment. He drowns his pain with alcohol, but the relief is only temporary. After the carnival closes, Max is approached by two young female audience members who want to party with the show's star. Before he can turn down the offer, the girls drag Max into their car and head back home for a night of partying.
The next day, Nick and Hank are called to the house to investigate the murder of the two women. The scene is bereft of conclusive evidence, but two carnival ticket stubs provide a lead for the detectives. They head to the carnival grounds and immediately notice the uncooperative attitude of the performers. The carnival leader, Hedig, gives Nick some background on the carnival. He's owned the establishment for 10 years, but he's confident that none of his employees are causing trouble.
After Nick and Hank depart, Max's girlfriend questions him about the death of the two women. Max says that he doesn't remember anything about that night, but he must have been responsible for the murder. Whatever happened last night, one thing is clear: the continuous forced woging is affecting Max's psychological health, and he's quickly falling apart.
Nick and Hank know that the carnival performers are Wesen, but it's usually against the rules for a Wesen to deliberately woge in front of a non-Wesen. The detectives decide to consult Monroe and Rosalee for more information. The carnival is technically not a violation of the Wesen Code of Swabia, since the spectators believe it to be a magic trick. But there's another danger to the carnival: umkippen.
Continuous repeated woging can lead to an ailment known as umkippen, in which the Wesen side eventually takes over, transforming the individual into an uncontrollable monster. It's a possible explanation for the two murder victims. If they took an umkippen-afflicted performer home with them, it's quite possible that he (or she) lost control and fell into a violent Wesen rage, murdering the women.
Monroe and Rosalee decide to investigate the carnival on their own. When they arrive, a carnival employee mistakes Rosalee for an auditioning performer. Before she can clarify her intentions, she's whisked onstage. After a quick woge demonstration for Hedig, she's given a part in the show. She'll perform tonight!
Monroe is uncomfortable with the situation, but they must find the umkippen-afflicted Wesen before he murders again. Behind the scenes, Rosalee quickly learns that the performers are abused and mistreated. She also learns that Hedig is a Lowen Wesen and that he was responsible for the murder of the two girls.
Meanwhile, Hank and Nick run background checks on all the performers. Unsolved murders seem to follow Max wherever he goes, making him the prime suspect in their murder case. Hank discovers a discrepancy, though: four mysterious murders happened before Max even joined the carnival. The only carnival member around for those murders was Hedig. Without a second to spare, Nick and Hank rush to the carnival grounds to arrest the Lowen and put an end to his murderous rampage.
Monroe, Hank and Nick are in the audience for the evening show, while Rosalee is onstage as a performer. During the finale of the routine, Max (in his Blutbad form) loses control and rampages through the crowd, with his sights set on Rosalee. Monroe woges to protect her and fights his fellow Blutbad one-on-one.
Monroe manages to restrain the Blutbad until he can transform back into his human form, and Monroe and Rosalee ensure Max that they will help him with his umkippen affliction. Meanwhile, Nick and Hank pursue Hedig, who dashes into a carnival fun house to elude the detectives. Unfortunately, Hedig's three mistreated performers corner him, and a quick breath of flames from his Damonfeuer performer ends the life of the murderous carnival owner. Justice has been served, Wesen-style.
Nick investigates a mysterious murder at a Wesen carnival.