Leo is at the Lubyanka, the MGB's super-scary lair. Even avowed tough guys like Leo are uncomfortable just being there—plus, he's still hung over from yesterday's drug-fueled bender.
Leo's boss, Major Kuzmin, assigns him to lead "Brodsky's interrogation," which is a first for Leo (2.7.35). Even worse, Vasili will be joining him.
Brodsky is sitting in a sparsely furnished room while a guard prods him to keep him awake. Leo tries to be friendly, explaining that Mikhail's daughters are going to an orphanage, but Brodsky scoffs—Soviet orphanages are harder to survive in than the streets.
Brodsky also denies that he's a spy. He didn't run from the MGB because he was guilty—he ran because he knew that he'd get convicted either way.
There's a knock at the door: it's Vasili and Doctor Roman Hvostov, an experienced interrogator. Hvostov leads Brodsky into a medical room, where he's strapped to a bed and injected with a "thick yellow oil" (2.7.104).
This stuff is camphor oil, which is used to induce seizures. And that it does. Presumably, Brodsky will have no choice but to tell the truth when he wakes up.
When Brodsky comes to, Leo asks him to name the people he works for. Without missing a beat, Brodsky rattles off a list of his veterinary clients.