And then he could do nothing, for perhaps a quarter of an hour, except listen. And even the listening was not especially good, since he was separated from what he was listening to by a deck of ceiling tiles that had been designed specifically to muffle sound. And the intruders, at least for the first little while, were trying to move stealthily; they had no idea whether anyone was in this office or what sort of reception they should expect, and so they had to clear the place. Clear it, in the sense of a military or police unit going through every room of a house to make sure that no attackers were hiding anywhere. From what little Sokolov could infer based on sounds, they seemed to know what they were doing; they were not just walking around like idiots, clumped together, poking their heads into offices, but rather leapfrogging each other from doorway to doorway and communicating in single-word utterances, or perhaps through sign language. They had, in other words, been through some sort of training. And they had to be armed; it would not make sense for them to do what they were doing unless they had guns and had them out and ready to fire.