In an expansive Oregon pasture, John, a young farmer, investigates a nighttime disturbance on his ranch. The farmer finds one of his cattle dead, his organs seemingly ripped from his body. Suddenly, he notices a glowing, blue creature staring at him in the distance and takes off for the gun in the trailer of his ATV. But when he turns around to protect himself against the mysterious figure, it attacks him and thrusts him up against a sharp metal object hanging off his vehicle. The creature runs away with a bag full of cow innards, just as Robert Hadley, the ranch owner, notices his dead ranch hand.
Monroe and Rosalee's relationship is better than ever, and as the two share a romantic moment at Monroe's house, Nick unceremoniously rushes in and kills the mood. Nick is in serious need of Monroe's help, as he's been working tirelessly to figure out the mystery behind the key he possesses. After Rosalee leaves, Nick shows Monroe his key, along with the occupying map, and Monroe notices a connection. Monroe's great-grandfather was a cartographer and has an ancient map of Swabia that looks very similar. When the two overlay the maps, it lines up perfectly with the Black Forest in Germany.
Elsewhere, the blue creature - a Gluhenvolk named Vincent - returns to his hideout in an abandoned barn, where his lover Jocelyn is eagerly waiting. Vincent delivers her the raw meat of the cattle, and Jocelyn ferociously devours it. She is pregnant with Vincent's child and he tells her to get some rest, as they'll have to move again soon. Jocelyn is distressed, as all the moving is tough on her body and she'd hoped they had settled in to their current hideout. Elsewhere, when an alien hunter hears about the cattle attack on the radio, he sets out for Portland.
Juliette is still struggling to fill in the gaps of her memory, particularly with her relationship with Nick. As she looks at an old photograph, Juliette goes back to a significant holiday party she attended with Nick. It's the first time they said, "I love you." Later on, Juliette visits Monroe with the photo she's used to help trigger old memories. She remembers her love for Nick, but worries she's treated him so badly Juliette's afraid she's scared him off for good. Monroe says the only thing Juliette can do is just tell Nick how she feels. She's not ready for that just yet, but Monroe lets Juliette know he's there if she ever needs anything. But when Juliette asks Monroe what a "Grimm" is, he's taken aback. Monroe doesn't really know what to say...
At the Precinct, Nick confronts Renard about the keys. The Captain tells Nick there are seven keys, of which the Royal families have four. Nick has one, which means two are unaccounted for; when all seven are merged, the location of a hidden treasure is revealed. Renard's ancestors tortured Nick's ancestor to get their hands on his key, and though no one knows what they lead to, some theories include the answer to alchemy, the sword of Muhammad or the nails from Christ's cross. For now, Renard wants to make sure his family keeps their hands off of Nick's key. All hold immense power for whomever finds them. Sgt. Wu interrupts with a new case - apparently an "alien life form" is mutilating cattle just outside of Portland, and the department needs Nick to investigate.
Meanwhile, Vincent's car won't start and he has to go find another car so he can escape detection with Jocelyn. She doesn't want him to leave her alone in the stable, but he doesn't have a choice. Vincent kisses her goodbye and promises he'll be back soon with a getaway vehicle. Later on, along a backcountry Oregon road, Vincent stands in the middle of the street morphed as a Gluhenvolk. When an unsuspecting driver turns the corner, the shock of his presence forces them off the road and into a nearby tree. Vincent steals the poor woman's car and drops her passed out body at his hideout before setting off with Jocelyn.
At the ranch where the "alien" attack occurred, the witness tells Nick he saw a glowing blue being run off in the distance after killing six cattle and his friend John. When Nick and Sgt. Wu check out the barbed wire fence surrounding the pasture, a small piece of blue skin is hanging off a post and the two catalogue it for testing. When the police leave the scene, they run into the alien hunter, George Lazure. He wants information on the alien and knows of similar attacks occurring all across the country. However, Sgt. Wu and Nick aren't interested in his help.
In the lab, forensics discovers luciferase in the skin sample Nick found at the farm. It's the chemical found in animals that produces bioluminescence, but this skin is distinctly human. Sgt. Wu calls Nick and lets him know they have a new witness, this time from the woman whose truck was stolen. While Nick talks to the victim, Sgt. Wu investigates similar cattle mutilations and finds a trend. They started two weeks ago in Nebraska and have been moving west ever since, the frequency and intensity picking up along the way. What is it about cows and aliens? Neither Nick nor Sgt. Wu has any idea.
After the police leave, George Lazure takes the opportunity to speak with the farmer who witnessed the alien attack. George shows the man a folder full of alien beings, hoping he'll identify one of the images as the creature he saw. Luckily for George, there's a match. With some leads, George eventually finds the barn where Vincent was recently hiding out in with Jocelyn. George gets a phone call from a business associate, who seems to have a vested interest in Jocelyn's baby. There are already four bidders waiting on the child, but George needs to find it first. Suddenly, George morphs into a Raub-Kondor.
On the road, Jocelyn's body can't take the bumps and turns of the winding back roads Vincent's driving on. If he doesn't immediately stop, she's going to have the baby right there in the backseat. Vincent pulls his car over and notices an abandoned cabin in the nearby woods. Inside, Vincent makes Jocelyn comfortable and starts a fire. She lets him know she's getting hungry again, which only means one thing. Vincent understands and sets out to find her food.
Sgt. Wu finally finds a connection between the cow mutilations and calls Nick with the update. The ovaries were taken from each killed animal. Nick goes to Rosalee in the Spice Shop for help, and she has an idea. Gluhenvolk are a Wesen species with roots in Africa, and the gestating female consumes cow ovaries when she is pregnant. Rosalee thinks there must be two: the pregnant female and her partner, who's responsible for the attacks. When Nick says there've been 27 attacks since the first one in Nebraska, Rosalee knows the Gluhenvolk is about to give birth any minute. Together with Monroe and Rosalee, Nick attempts to predict where the Gluhenvolk will strike next.
Vincent finds a nearby farm full of cows that can satisfy Jocelyn's gestational cravings, but George is now one step ahead of him. Morphing into a Raub-Kondor, George steps out of his nearby trailer with a rifle, ready to attack. When Nick, Monroe and Rosalee arrive at the same scene, Nick immediately notices George's vehicle, but no one's inside. When searching around the trailer, Monroe and Rosalee quickly realize George is not a "UFO-oligist." They realize this guy hunts Wesen with a special gun that keeps its victims fully morphed after death. George operates on their bodies in his trailer and sells the taxidermy'd remains to the highest bidder. Nick and his friends rush out to get to the Gluhenvolk before George kills him.
On the farm, George shoots at a wandering Vincent and hits the bag in his hand, blood from the stolen ovaries bursting everywhere. Vincent escapes with his life before George can reach him. Nick and his group discover Jocelyn at the abandoned cabin and accidentally shock the poor girl into labor. Rosalee jumps into action to help deliver the Gluhenvolk baby. Right before the baby comes out, Vincent arrives just in time to see his child's birth. The baby is beautiful and healthy, and it's glowing a beautiful blue. As the group revels in the miracle of the Gluhenvolk birth, a species long-thought to be extinct in the Grimm world, George bursts into the cabin with his gun, ready to take the baby for his own...
Rosalee, Vincent and Monroe all morph into their respective Wesen forms to help protect the baby, but George is not deterred. But when Nick mentions he's a Grimm, Monroe seizes the opportunity to attack and a fight breaks out as George morphs into a Raub-Kondor. When George knocks Monroe out, he turns around, only to be shot and killed with his own special gun by Nick. Monroe and Rosalee see Vincent and Jocelyn off, as the two travel to Alaska to meet up with the few remaining Gluhenvolk's remaining. Later on, a SWAT team descends on the cabin to find George dead in his car but fully morphed. They think they've found the alien, but when they step back, the drug from his gun wears off and his body demorphs...