Animal rights activists break into a testing lab to free all the innocent beasts therein, only they open a door to an animal's cage, one who's really sick of having its eyes jabbed with mascara brushes. It violently attacks and kills the lab worker who responds to a tripped alarm, kills one of the activists on site, and then chases down and kills the other three activists, even though they're in a car.

So the Fringe team investigates, because the wounds indicate some kind of freaky animal not indigenous to the area (fang marks four full inches apart, huge claws), and they hit on the idea of some sort of genetic hybrid. Naturally, Walter did some work in that vein a few decades ago, so he thinks this is one of those "someone carried on my work" cases.

So he feels guilty when Charlie is hurt checking out an Animal Control report of a "monster" sighting. Worse news: one of the dead activists busts out all over with the larvae of the unleashed creature. Seems the monster lays its eggs in its victims using its tail. An ultrasound confirms there are plenty of the little critters swimming around Charlie's insides, and the best idea Walter has for getting rid of them is to inject Charlie with the blood of the creature, because his theory is that if the parasitic larvae think they're feeding off one of their own, they'll stop feeding, and die.

So no problem: just catch this thing, right? Like in The Host. Olivia's investigation discovers one of the activists was the son of a geneticist at a nearby lab. He tries covering up the genetic experimentation, but soon withers under Olivia's sunny determination, and provides the team with the monster's genetic makeup. It's part bat, which are highly maternal creatures, so Walter and the team head into the sewers -- which is how the animal's moving throughout the city -- to bait it using its own larvae.

Walter, despite finding out his work was not to blame for the current monstrosity, recklessly tries to take care of the creature himself, by ingesting poison that will kill the creature if he's devoured. Fortunately, the animal winds up being brought down by a couple of gunshots, and the blood is used to cure Charlie, who can go home to his wife and her terrible jokes.

Oh, and Peter and Rachel are spending time chatting on the phone, about -- among other things -- that ridiculously annoying "if you like pina coladas" song, which might be the weirdest aspect of the whole episode.

Discuss this episode in our forums, then see vlogger Sean Crespo's possibly more twisted take on Fringe in No Prior Knowledge!