The will to conquer is the first condition of victory.
At Monroe's house, Nick and Monroe watch the news broadcast of Renard's press conference. Monroe realizes that the man he has identified as Juliette's lover is someone that Nick knows. As Nick goes off to confront his superior, Monroe tries to stop him. Nick gets a call and tells his friend that the four Verrat agents that they killed earlier have been found and he's been called to the crime scene.
Renard brings in a Scharfblicke Wesen named Al Eckert. The man, a locksmith, transforms into his owl form and scans the lock, and then produces the proper skeleton key for Renard. Renard tells Al to forget he was there and the Scharfblicke to leave. Once he goes, Renard enters the trailer and looks for they key, but is interrupted when he receives a call about a case.
At the crime scene, Wu tells Nick that the killer or killers didn't leave any traces. Renard arrives and Nick eyes him angrily, and they go over the bodies. Nick suggests that they came there to kill their intended victim, who caught them by surprise and fought back. Wu notices a distinctive tattoo on the palm of each victim and Nick reminds them that Waltz, a corpse they found eight months ago, had the same tattoo. Juliette calls Renard and tells him that Nick has moved out, and asks him to come over and help her understand what's going on. The captain says that he'll be there as soon as he can.
The trio returns to the office and Renard goes to the office to call the Castle spy in Vienna. The man says that one of their members, Jacques, is dead, and Renard tells him to learn if his brother sent the four Verrat agents. Nick and Wu come in with video footage of the hotel where the dead agents were staying. They watch and see Monroe leave the hotel first and then the four victims follow him. Nick claims that Monroe couldn't have killed the victims and insists that he isn't a suspect. Renard complains about a headache and Nick and Wu leave him.
Monroe is working at home when Rosalee calls him. He tells her what has been going on and that Renard and Juliette are the ones with the romantic compulsion. Rosalee explains that the compulsion means that the two of them can't resist the compulsion. Monroe worries that he can't find an antidote and Rosalee tells him that since her aunt is doing better, she's catching the next bus back to Portland.
Renard goes to see Juliette while Nick secretly follows him. The couple kisses at the doorstep and then Renard goes inside. Nick starts to walk up but is interrupted when Monroe calls him. The Blutbad explains that Renard and Juliette don't have a choice, and that Juliette would still be in the coma if Renard hadn't helped her. Unaware of where Nick is, Monroe apologizes for calling, figuring that Nick is still at the precinct house. Nick doesn't correct his friend's mistakes, but he then walks away.
Inside the house, Renard and Juliette start to tear their clothing off as they kiss.
Nick goes back to Monroe's house and the Blutbad tells him that Renard came to the spice shop to find an antidote to his feelings. Monroe admits that if he had just provided the cure and never told Nick, none of what followed would have happened and everything would have been fine. He also tells Nick that a Hexenbeist came into the shop to get ingredients for a potion similar to the one that Renard must have used and figures that she's involved.
Renard and Juliette end up hitting and biting each other, and Juliette finally tells him to get out as they both struggle against the compulsion. As he fights the feelings, Renard's face starts to change. Juliette finally grabs a gun and fires several shots into the ceiling. Renard runs out and goes to his car, driving off before the police can respond to the gunshots.
Nick and Monroe go to the spice shop and look for the ingredient list that the Hexenbeist brought in. When they find it, Nick realizes from the phone number that it belongs to Adalind's mother, Catherine. He realizes that she must have set up the spell to drive Juliette and Renard into each other's arms. When Monroe suggests that they talk to Catherine, Nick admits that his mother killed Catherine before she left town. Wu calls to tell Nick that someone fired shot at his home and tore up the house. Juliette isn't saying anything, and Nick says that he'll be there shortly.
Officer Winger goes to Adalind's cell and tells her that she's being released. Adalind demands to know who's responsible but Winger says that she doesn't know and orders her out.
When Nick returns home, he tries to get answers from Juliette. All she will say is that an intruder broke in and fired shots, taking the gun with him. She wonders what is happening and Nick tells her that he knows who she's involved with. He then tells Wu to write up the shooting as self-defense and asks the sergeant to put someone on guard at the house.
Adalind walks out of the police station and walks down the street. Renard finally grabs her, says that they need to talk, and drags her to his car. As he drives off, he tells Adalind that he's found the trailer.
Nick goes back to see Monroe and updates him on what happened. They figure that if Juliette wanted to kill Renard then she had the perfect opportunity but didn't take it. Monroe suggests that Nick get some sleep but realizes that his friend won't take his advice.
Renard drives Adalind into the woods and orders her to break the compulsion. She points out that she can't since Nick took her powers, but she does have a way to make Renard feel better. He tries to slap her, realizing what she means, but Adalind stops him and says that he'll have to trust her. They start to kiss and Adalind tells Renard to show her his real face, the one that he can never show to Juliette. Relieved, Renard woges, revealing his partial Hexenbeist features, and they rip off each other's clothing.
Rosalee arrives in town the next morning and Nick and Monroe are at the bus station to greet her. She immediately runs over to kiss Monroe and then says that they need to go to the spice shop now that she knows what the problem is.
Adalind is at Renard's apartment when he emerges from the bedroom. He warns her that he'll be in trouble if his brother gets the key, and suggests that she choose sides. Adalind says that she chose him a long time ago but he turned her back on her. Renard admits that he underestimated her and tells her to make herself at home until he returns.
At the spice shop, Rosalee works out that if the potion allowed Renard to break the curse then the captain must be the Royal in Portland. She warns Nick that Juliette and Renard will kill each other if the curse progresses much further and they start looking through the books to find a cure.
Renard goes back to Marie's trailer and looks for the key without success. When he fails to find it, Renard tries to work out where else Nick might have hidden it and remembers the Grimm putting something in his desk at the station.
Monroe finally finds the cure in one of the books but when Rosalee reads it, she realizes that Juliette and Renard will have to take it together. Nick tells his friends that he'll get them there but Rosalee warns him that they also need the original source of the infection. When Nick wonders what happened to the cat, Rosalee admits that it went berserk, escaped, and was hit by a car. Nick wonders what they can do without it and Rosalee shows him a passage in the book that reveals the next step.
Renard goes back to the station and searches through Nick's desk. He finds the key in a drawer and pockets it, just as Hank comes in and asks where Nick is. Renard claims that he was looking for Nick's file on Adalind and points out that she was connected to the men that beat Hank. The captain warns Hank to watch his back and Hank assures him that he'll keep an eye out.
At the spice shop, Rosalee finishes mixing the purification potion that Renard used. She tells Nick that drinking it is the first of two steps and the other one will require Juliette and Renard. Before Nick can drink it, Hank calls to tell Nick that he saw Renard going through his partner's desk. Nick tells Hank that he's on his way and to stall Renard as long as he can. He then tells Rosalee and Monroe that he'll have to drink the potion later.
Renard takes the key into his office and uses ink to bring out the stamp-like impression. Once he has the portion of the map on paper, he hides the key in his desk and tries to leave. Hank stops him, asking about Adalind, but Renard brushes past him and goes back to his apartment. As he walks down the hallway, Juliette calls him and says that Nick knows Renard is the man she's involved with. She hangs up and Renard goes inside, where Adalind asks him about the key. Renard lies and says that he didn't find it, and Adalind warns him that his brother has a car waiting for her outside. She thanks Renard for the night together and leaves, and Renard takes the key out of his pocket.
Nick arrives at the station and makes sure that the key is no longer in his desk. When Hank finds him, he tells Nick that Adalind was released. They leave the station and Nick tells Hank to find Adalind while he deals with Renard. As Nick gets in his car, Renard calls him and asks to talk.
That night, Nick drives out to the abandoned house where the Postman, the first Wesen he encountered, once lived. Renard pulls up and starts to explain, and Nick attacks him. The captain tries to stop him, insisting that they don't have to fight, but Nick presses his attack. Renard loses control, revealing his half-Hexenbeist true face, and tells Nick that the only thing that matters is the key. He gives Nick the key back and tells the Grimm that even if one of them kills the other, it won't end. Adalind will kill both of them to get the key for Renard's brother. When Nick asks about Juliette, Renard insists that he wants to end the compulsion as much as Nick does. He offers to prove his good intentions if he knew of a way, and Nick says that he has an idea.
Later, Juliette answers the door and finds Nick and Renard at her step. They go to the spice shop and Rosalee gives Nick the purification potion. He drinks it and after a few seconds, collapses to the floor as his house turns a bright red. Juliette runs to his side and begs Rosalee to do something.
In Vienna, Adalind runs a home pregnancy test and confirms that she's pregnant with Renard's child.