I hear Mrs.Trenor wants to build out a new ball-room, and that divergence from Gus on that point keeps her at Bellomont.

The dimensions of the Brys' ball-room must rankle: you may be sure she knows 'em as well as if she'd been there last night with a yard-measure.

Who said she was in town, by the way?
That Farish boy?
She isn't, I know; Mrs.Stepney was right; the house is dark, you see: I suppose Gus lives in the back." He had halted opposite the Trenors' corner, and Selden perforce stayed his steps also.

The house loomed obscure and uninhabited; only an oblong gleam above the door spoke of provisional occupancy.
"They've bought the house at the back: it gives them a hundred and fifty feet in the side street.

There's where the ball-room's to be, with a gallery connecting it: billiard-room and so on above.