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

A man descends into the sewers of Portland carrying a bag full of stolen items.

In Vienna, Adalind meets with Prince Viktor, Eric’s second cousin on his mother side. Viktor promises Adalind that he will find whatever men–or women–who were responsible for Eric’s death and see to their punishment. Meanwhile, he tells Adalind that he wants to retain her legal services, and notes that he is well aware that she had an intimate relationship with Eric. Viktor then asks Adalind what she knows about Sean Renard, his half-cousin living in Portland, and the Grimm, Nicholas Burkhardt. She admits that she knows something about them and Viktor tells her to put together a list of anyone in Portland that might have been involved in Eric’s murder.

A man breaks into the Himber home and starts taking things. Scott Himber drives in from the airport and calls his mother, and tells her that he just arrived in town. When he goes inside, he realizes that someone has been going through the place. The thief comes at him and Scott runs to the kitchen and grabs a knife. However, the intruder disarms him and transforms into an alligator-like Wesen, and then tears Scott apart.

When Scott’s corpse is found, Nick and Hank arrive at the house and investigate the murder. The killer ripped off Scott’s arm and left huge footprints, and Nick wonders if they’re dealing with a Siegbarste. They head back to the station and confirmed when Scott arrived, and alibi the taxi driver that dropped him off. Hank starts checking pawnshops to see if anyone sold the stolen goods while Nick meets with Dr. Harper. She finishes examining Scott’s body and tells Nick that although Scott’s arm was ripped off, he was killed when the murderer shook him so violently that he broke his neck.

Sewer worker Charlie Heller suits up his co-worker Jimmy to head down into the sewers to check a blockage. Jimmy goes down on a line and finds a tree blocking the line, and tells Charlie over the radio to get a chainsaw. As he waits, Jimmy hears something moving in the darkness. A creature attacks him and up above, the safety line is jerked all the way out. Charlie tells the other workers to pull Jimmy up. When they do, they discover that Jimmy is dead and his leg is missing.

In Vienna, Renard waits for the Resistance to set up the meeting time and place. Sebastien visits the warehouse where Renard is holed up with Meisner and brings some supplies. They explain that someone betrayed them to the Verrat and wonder if Sebastien was involved, but he assures them that he’s loyal. Sebastien then tells Renard that Viktor arrived two days ago and that the Family are grooming him to take Eric’s place, and that Viktor plans to find Eric’s killer. They receive word that the Resistance is meeting the next night and that their leader, Tavitian, is eager to meet with Renard. Satisfied that Sebastien is loyal, Meisner heads out to get more ammunition while Renard waits.

Nick and Hank arrive at the manhole and interview Charlie, who confirms that Jimmy was on his own and in constant radio contact. The Deputy ME examines Jimmy’s corpse and tells the detectives that the only time he’s seen similar injuries was when a bear attacked a man. Wu suggests that it’s an alligator attack and mentions the urban legend of alligators living in the sewers. Charlie takes Nick, Hank, and Wu down to inspect where Jimmy was killed, and Wu admits that he’s claustrophobic. He continues on with them and they find the spot where Jimmy was killed. Lying nearby is a backpack filled with stolen items. While Wu checks the spot, Nick and the others head off, but the street noises are too loud for Nick to pick up anything with his enhanced hearing. Meanwhile, Wu checks around where Jimmy was killed and sees something wedged into the floor. He tries to pull it up, falls, and lands on Jimmy’s severed leg.

Back at the station, Nick and Hank go over the backpack’s contents with Wu and confirm that they belonged to home owners targeted in a recent series of robberies. They check the pattern and discover that the thief hits a particular neighborhood for a week or so and then moves on when the police start to catch up. They find a gym card belonging to Scott, confirming that the same thief is responsible for his murder. The ME calls Nick and tells him that the bite pattern on Jimmy’s leg matches that of an alligator.

That night, Nick and Hank go to Monroe’s house to consult with him. He recognizes the description as that of a Gelumcaedus, a rarely-seen Wesen, but says that he can’t go with them to the trailer because he’s working on dinner. When the detectives play dumb, Monroe gives in and tells them to bring the journals there along with Juliette and they’ll have dinner and look through the journals together.

In Vienna, Sebastien returns to the warehouse and tells Renard that Claude Frenay, one of the Resistance leaders, is ready to meet with them. Renard grabs his guns and heads out with Sebastien and Meisner.

Rosalee joins the others and they find a reference to a Gelumcaedus in the sewers of London in the 19th century. The Grimm of that time used a primitive breathing apparatus to go into the sewers and confront the Wesen. The Gelumcaedus are one of the oldest documented Wesen, and they served as Praetorian soldiers with the Romans. When Rome fell, the Gelumcaedi retreated into the waterways and disappeared. Juliette finds a reference to a bracer with an extendible blade, a Vambrace, which the Grimm used to fight the Gelumcaedus. Nick remembers that it’s in Aunt Marie’s cabinet of weapons, and they figure that they’re dealing with a Gelumcaedus.

The next day, Nick and Hank meet with a B.E.S. consultant to get information on Portland’s sewer systems. She points out that the outfalls leading into the river are large enough for man to walk in. She leaves them with the maps and the detectives work out where the outfalls are near the various neighborhoods where the robberies occur. Jimmy was killed near the Sheridan Outfall, which links to the other outfalls, and the partners figure the Gelumcaedus is lurking there. Nick goes to the trailer and gets the Vambrace while Hank equips himself with a shotgun. As Nick checks the blade on the Vambrace, he has a memory-flash of the man at the bar attacking him when he was under the drug’s influence. Once the memory fade, Nick tells Hank that they’re ready.

The detectives approach the Sheridan Outfall and spot large footprints leading into it. They go inside, following the maps, and Nick hears someone moving ahead of them. They spot him and give chase, but are forced to retrace their steps when they lose their target. Nick finds a hidden door leading to another part of the sewers, and the partners follow it to a hidden chamber containing more stolen items as well as a cot. The Gelumcaedus comes in behind them and attacks them, throwing Hank into a wall. It turns on Nick, who uses the Vambrace on his arm to block its teeth, and Hank recovers and the two officers club the Wesen down. As it stares at Nick, it mutters the word “decapitare.”

Renard drives to a manor in neighboring France and arrives at a country home. One of the Resistance members greets Renard and tells him that their meeting has been delayed because of the trial. A man screams from a nearby barn and the Resistance members take Renard inside. Frenay is there, torturing the man who betrayed them, Constantine Breslau. Once Breslau gives Frenay the name of the woman he was answering to, Frenay has a Resistance member take the traitor out to be shot. Frenay then greets Renard, who thanks him for saving his mother’s life years ago. A shot rings out and Frenay tells Renard that they’ll begin the meeting as soon as Tavitian arrives.

At the station, Nick and Hank interrogate the Gelumcaedus, Gregorek. They have his file and know he’s been arrested in two other cities for robbery but was turned loose due to lack of evidence. The detectives figure they can eventually tie him to murders in the other cities, but Gregorek, unconcerned, just tells them to stop wasting his time. Outside, the detectives wonder why Gregorek isn’t worried. Hank heads for home while Nick calls Monroe to ask for advice. Rosalee answers and when Nick tells her what Gregorek said, explains that “decapitare” is Latin for “Grimm.”

After checking the crime reports, Nick calls Hank as his partner arrives at home. The Grimm warns that the times of the robberies overlap, meaning that Gregorek isn’t working alone. After Hank hangs up, a second Gelumcaedus attacks him and drags him into the sewers. When Nick stops by later, he discovers that Hank is gone. The second Gelumcaedus, Andre, calls Nick on Hank’s cellphone and tells him to release Gregorek in return for Hank’s life. Nick goes back to the station and releases Gregorek at gunpoint. The Grimm warns the Gelumcaedus that if anything happens to Hank then the Wesen won’t be dealing with a cop.

Nick takes Gregorek to the Outfall and Andre calls him again. Once Nick confirms that Hank is okay, he hangs up and Gregorek says that his brother has already taken care of him. Nick leads the Gelumcaedus into the sewers where they meet with Andre, who has Hank tied to a wall. They make the exchange and Gregorek tells his brother that they’re dealing with a Grimm. Nick removes the gag from Hank, who yells that there’s a third Gelumcaedus. The third Wesen attacks Nick and a fight breaks out. Nick manages to kill Andre and the other brother, while Hank knocks out Gregorek with a pipe.

In Vienna, Adalind is in her hotel room and admires her pregnancy in the mirror. As the black spider symbol appears briefly on her stomach, Viktor watches via a hidden camera and smiles in satisfaction.

Nick goes back to the trailer and puts the Vambrace away, and admits that he likes being known as a decapitare.