When the burden and its bearers, with Anderson in the rear, reached the doorway into the hall, Lizzie shrank before the sight, affrighted, and turned toward the alcove while Miss Cornelia stared unseeingly out toward the front windows.

So, for perhaps a dozen ticks of time Dale was left unwatched--and she made the most of her opportunity.
Her fingers fumbled at the bosom of her dress--she took out the precious, dangerous fragment of blue-print that Anderson must not find in her possession--but where to hide it, before her chance had passed?
Her eyes fell on the bread roll that had fallen from the detective's supper tray to the floor when Lizzie had seen the gleaming eye on the stairs and had lain there unnoticed ever since.

She bent over swiftly and secreted the tantalizing scrap of blue paper in the body of the roll, smoothing the crust back above it with trembling fingers.

Then she replaced the roll where it had fallen originally and straightened up just as Billy and the detective returned.
Billy went immediately to the tray, picked it up, and started to go out again.

Then he noticed the roll on the floor, stooped for it, and replaced it upon the tray.