"But for the pit confounders, let them go, and find as little mercy as they show!"

A person walks through the sewers with a full bag. He walks up to a couple of filled barrels and dumps the new items into one of them.

In Vienna, Adalind is greeted by the new Prince, Viktor Chlodwig zu Schellendorf von Konigsburg. He tells her he wants to find out who is responsible for Eric's death, seemingly sincerely determined to avenge his late cousin. Viktor notes that while the police in Vienna are putting together a list of suspects, he has his own list as well, and he suspects that whatever happened with Eric in Portland had consequences upon his return to Vienna. He confirms with Adalind that she has spent some time in Portland and that she knows both Sean Renard and the Grimm, Nick Burkhardt. He then tells Adalind to put a list together of everyone in Portland who may have had something to do with Eric's death.

In Portland, a man, Gregorek, breaks into a house and starts taking items from the house, such as candle holders and China plates, making a huge mess. Hearing a voice from outside, he pauses and sees a person being dropped off in front of the house. When the person enters and notices the mess, Gregorek woges into a reptilian Wesen and attacks.

Nick and Hank arrive to the scene of the attack and find the bloodied body of Scott Himber. One of Scott's arms is torn out of its socket. Nick notices footprints in the blood and says they are size 15 or bigger. He tells Hank they may be dealing with a Siegbarste again because someone or something has to be very strong to take someone's arm off.

Nick and Hank go to the precinct and research the victim and similar crimes. They find that there have been two other reported break-ins at houses in the last week, one near Scott's house. The M.E. calls to let them know they are ready for them. Hank says he'll check pawn shops in hopes of connecting all three robberies, while Nick talks to the M.E.

At the Medical Examiner's Office, Harper tells Nick that Scott's humerus was ripped clean from the socket. The force of the bite on Scott's arm crushed the ulna and the radius, causing the broken neck which killed him. Harper says whatever got a hold of him gave him a good shaking because there are multiple fractures of the long bones and a subdural hematoma, which is bleeding in the brain.

Jeremy, a city worker, is lowered into a manhole by his partner, Charlie, to clear a blockage. Upon finding it, he hears a noise down further in the sewers and goes to check it out, when he is attacked from behind. The reel above ground that Jeremy's line is connected to starts spinning wildly. Charlie calls out to Jimmy via radio, but gets no answer. They reel Jeremy out to find that he is dead and missing a leg.

In Vienna, Sebastien drives up to an abandoned building, as he walks into the building, a gun is pointed at his head by Renard. Meisner then comes through the door telling Renard that Sebastien is alone. Renard tells Sebastien "I would have regretted shooting you, unless you were the one who set us up when the Verrat tried to kill us." Sebastien retorts that he wasn't even aware of where they were and that Breslau was the one who arranged it all. Sebastien tells Renard his cousin, Viktor, arrived a couple days ago, and the Family wants him to take Eric's place. Renard says he doesn't know much about him other than the fact Eric never trusted him. Sebastien explains he is looking for who is responsible for killing Eric. Renard asks Sebastien when the meeting is, which Sebastien says he doesn't know where, but he knows it is at midnight tomorrow and that Frenay and Tavitian will be there. Sebastien tells Renard that Tavitian wants to meet him, and some think Tavitian was involved in Eric's death.

The police, including Nick, Hank, and Wu, arrive to the scene of Jeremy's death. Charlie tells Nick and Hank that Jeremy was in the sewers no more than 5 minutes. Explaining that this is the first time since he's been on the job that anyone has died. Wu tells Nick and Hank that the Deputy Medical Examiner is ready for them. The M.E. shows them the wounds and says he's only seen something like this when someone was attacked by a bear. Wu jokes "Alligator in the sewers anyone?"

Charlie takes Nick, Hank, and Wu to the sewers so they can have a look around. They come across the blockage and notice blood on the walls. Hank spots a backpack in the water and gives it to Wu to take back to the surface. Nick, Hank, and Charlie continue past the blockage while Wu looks around the blockage. He finds more bags and sees something sticking slightly out of the water. He goes to grab it, but it won't budge. Pulling harder he gets it unstuck, and falls backwards. Looking down he sees that the item was Jimmy's leg and freaks out.

Back at the precinct, Nick, Hank, and Wu research and find that the items in the backpacks match the robberies reported around the neighborhood. They doubt that the sewer murder could be linked to Scott's, until Wu finds Scott's gym card in one of the packs. Nick gets a call and learns that the bite marks on Jimmy's leg most closely match an alligator. Wu comments that "alligators don't rob houses." Which Nick and Hank exchange a look.

Nick and Hank go to Monroe's house to discuss the possibility of a Wesen that "lives underground and can rip limbs like taffy." Monroe tells them it's not a gator, and Nick suggests a Siegbarste, but Monroe tells him tight spaces make them irritable. Monroe tells them that it's most likely a Gelumcaedus and tells them to go to the trailer to get some books and bring them back. He invites them for dinner and tells Nick to bring Juliette and Rhett as well.

Sebastien returns to the warehouse and is met again with guns. He informs Renard and Meisner that Frenay wants them there at the meeting now and they must leave at once.

Nick, Hank, Monroe, Rosalee, and Juliette lounge around in the living room, each with a book. While Rhett is in a play pen, they learn that Gelumcaedus are an ancient species, hired to protect aqueducts in the Roman Empire. In one of the journals, a hunter's arms were torn off in a fight with a Gelumcaedus as it is nearly impossible to escape a Gelumcaedus' grip. This led the Grimms to procure a vambrace in case of future battles with a Gelumcaedus.  "Hey I have one in the trailer." Hank sarcastically scoffs. Nick and Hank agree they have to go back to the sewers, but not as cops.

The duo do more research on the sewers and acquire a map from a B.E.S. Contractor. They realize that the tunnels intersect around where the robberies and murders have occurred and that the Gelumcaedus is using them as a way to get around the city.

In the trailer, Nick digs out the vambrace from the weapons cabinet. Nick shows Hank the image of the Gelumcaedus on the vambrace and asks Hank if he wants to wear it. Hank declines Nick's offer, preferring to "go 21st century" with a rifle. Nick decides to wear it in honor of his ancestors and surprises both of them when a blade shoots out of the brace. When Nick sees the hidden blade come out, it brings back the memory of the bar fight customer pulling a knife on him when he was infected with the Cracher-Mortel toxin.

Nick and Hank re-enter the sewers. They walk for awhile with Nick checking the map, when hears what he thinks is breathing and looks around. A figure runs by down one of the tunnels, and they chase after it. They lose him, however, as Nick is confused by the footsteps he hears, since they sound like they are in 2 or 3 places at once. Hank says it's probably the echo, and Nick says since they aren't sure which tunnel to go down, they need to retrace their steps. Nick soon catches the sound of ticking, a lot of ticking, and discovers a door in the wall of the sewer. Opening it to find the Gelumcaedus' hideout, complete with a bed, many clocks, and other various items. Hank is attacked from behind by the Gelumcaedus and is thrown into a shelf. The Gelumcaedus manages to bite down on Nick's arm, but the vambrace protects him, and the Gelumcaedus throws Nick to the ground. Before the Gelumcaedus can attack Nick, Hank hits him in the back with his rifle, knocking him down. Nick quickly stands up as Hank warns the Gelumcaedus not to move. The Gelumcaedus woges back into his human form, revealing himself to be Gregorek. "Decapitare." he snarls at Nick, clearly taken aback, and not expecting a Grimm.

Renard, Sebastien and Meisner arrive to the meeting place where they are greeted by Franz and another man. Franz tells them that a "trial" is ongoing, and they hear pained shouts in the distance. Renard comments that they must have reached a verdict. Entering a barn, they see Breslau, the man who set up the "safehouse" for Renard and Meisner, being interrogated violently by Frenay. Frenay beseeches Breslau to tell him what "her" name is, not wanting to hurt him more than necessary. Frenay says that even though Breslau did not know the woman was working for the Verrat, he should have known. Breslau finally complies and whispers the woman's name as Frenay leans forward to hear. Frenay walks to Meisner, handing him a gun. He tells him Breslau betrayed them all and asks Meisner if he would prefer someone else to kill Breslau, but Meisner says no. Breslau complies and is led outside, and Frenay shakes hands with Sebastien and Renard. Renard comments that Frenay saved his mother once, and Frenay tells him, "It's good to have you with us," as a gunshot rings out signifying Meisner killing Breslau.

Gregorek is handcuffed in a precinct interrogation room. Nick and Hank attempt to get a confession from him, but he refuses to admit to anything. Nick and Hank leave the room and both say they're calling it a night. Hank leaves, and Nick says he needs to call Monroe first. Rosalee picks up and tells Nick that Monroe is knee deep in a clock. She puts Nick on speaker, and he asks what "Decapitare" means. Rosalee explains that it is the Latin name used for Grimms, as in "he who decapitates."

Nick realizes that the times of the robberies overlap, which means Gregorek was not working alone. He calls Hank and informs him about the new info. Nick plans to cross reference the reports, and if he finds something he'll come over. As soon as Hank hangs up, he is attacked from behind by a Gelumcaedus. Hank is bound, gagged, and dragged into the sewers.

Nick arrives at Hank's house. he knocks a couple times without an answer when he receives a call from Hank's phone, but it is instead a stranger on the other side. The stranger demands Gregorek back and threatens to rip Hank into pieces. Distressed, Nick demands to talk to Hank, but the man hangs up. Nick gets Gregorek and brings him to the sewers, where he receives another call from the man who took Hank. Nick tells him if he doesn't hear Hank's voice, he'll shoot Gregorek. So he puts Hank on the phone long enough just to say Nick's name. The man tells Nick to leave his gun in the car and bring "my brother to me."

In the sewers, Gregorek comments on how he had been frightened of the Decapitare as a child when his grandfather used to scare him with stories. He adds that Nick doesn't seem so scary, and Gregorek's brother, Andre, waits deep in the sewers with an immobilized Hank. Demanding Nick to free Gregorek, or he will cut Hank's throat. Nick complies right away, and they exchange hostages. Nick frees Hank while Gregorek informs Andre about Nick being Decapitare, and Andre looks at Nick in a new perspective. The brothers decide that they cannot allow Nick and Hank to escape alive. As soon as the tape on Hank's mouth is removed he tells Nick, "There's three brothers". A third Gelumcaedus attacks Nick from behind as Andre and Gregorek woge. Nick manages to knock down the third brother as Hank struggles to get free. The other two brothers lunge, but Andre is quickly overwhelmed. Nick slits his throat swiftly with the vambrace's blade, using the corpse as leverage and stabbing the other brother too. Gregorek pins Nick to the wall, but Hank hits him with a pole, and the duo once more subdue him. Gregorek is devastated by the death of his brothers, but Nick and Hank are emotionless.

Adalind whispers to her baby, seeming to imagine what her child will call her in the future. She rubs more of the substance she made with Stefania with Frau Pech's body. She rubs the substance on her stomach, and it take the shape of a spider before absorbing into her skin. Viktor watches her from hidden cameras while she stands in front of the mirror.

Nick puts the vambrace back into the trailer's closet. He says to himself, "Decapitare. I kinda like that," and closes the weapons cabinet.

Walking out of the trailer, he heads to his jeep, getting in and driving home. When he gets home, he enters and smells food cooking. Walking toward the kitchen, he finds Juliette cooking Chicken Wings for supper. Turning to feed Rhett, Juliette notices Nick standing there, and walks over to him. They share a kiss and Juliette orders him to go clean up before turning to feed Rhett again. Getting back from freshening up, he walks over and takes over feeding Rhett while Juliette makes her own plate. They sit down and enjoy a nice dinner together with Rhett.