Then Astrid comes in, brightly telling them Walter wants to know which of them has "fearless nasal passages" which would make any sane person run screaming.

Out in the lab, Walter is giving a lecture on the history of perfumery, explaining that for centuries perfumers would use a "single, disparate rancid note" to counterbalance the other "sweet and unctuous" scents in a fragrance, such as the Greeks using carcasses and the Egyptians using afterbirth.

Olivia's all, "So this guy's making a perfume?" and Walter, by now used to the fact that his history lessons make everyone miss the point, says that the compound the killer used has a single rancid note: castoreum, which comes from the aforementioned beaver sacs. Walter offers Lincoln and Olivia a whiff, but they're warned off by Astrid. Anyway, Astrid tells them that castoreum is relatively easy to trace; only five perfume manufacturers use it, so the field agents divvy them up and get going.

Over at the Observer's apartment, Peter's poking around some old newspapers when a persistent beeping gets his attention. He opens the lid of a nearby cabinet that reveals an old record player, which looks to have been manufactured before beeping was invented. He pokes around until he accidentally finds the secret switch that lifts up the record player, revealing a briefcase hidden underneath.

He pops the locks and finds inside the standard-issue Observer snap-open binocular scanner thing. He takes a peek through it, surveys the room and then picks up the thing that's making the beeping: a little handheld device with a green screen with a dot on it. Maybe you can find ghosts with that!

Meanwhile, Astrid appears to be checking perfume manufacturers by herself while Lincoln and Olivia need to do it together. They're leaving "Scentax" having come up empty, when Astrid calls to tell them that Empire World Fragrance recently fired one of its employees, Anson Carr, for stealing castoreum. She's looking at the file now: there's Scarface, all right!

Meanwhile, in Chelsea, some poor bastard is locked inside Anson Scarrface's dehydration chamber of death, screaming to be let out. Unfortunately for him, it appears to be soundproof, so Scarrface goes about his work, adjusting knobs and levers in peace. Also, he's playing some new-agey pop by Jon and Vangelis, somehow making the human goop he's collecting all the creepier. It's a mad scientist montage, set to a tinkly piano and then we get a glimpse at the motivation: from a little box, Scarrface pulls out an old picture of a woman. It's always about a woman, isn't it? Every time you hear about a psycho killing men and extracting their pheromones to create a chemical compound to seduce their wives and then killing them too, it's ALWAYS about a woman.