When he had finished he turned patiently toward the billiard room--the little flame of his candle was swallowed up in its dark recesses--he closed the door of the living-room behind him.

The storm was dying away now, but a few flashes of lightning still flickered, lighting up the darkness of the deserted living-room now and then with a harsh, brief glare.
A lightning flash--a shadow cast abruptly on the shade of one of the French windows, to disappear as abruptly as the flash was blotted out--the shadow of a man--a prowler--feeling his way through the lightning-slashed darkness to the terrace door.

The detective?
Brooks?
The Bat?
The lightning flash was too brief for any observer to have recognized the stealing shape--if any observer had been there.
But the lack of an observer was promptly remedied.

Just as the shadowy shape reached the terrace door and its shadow-fingers closed over the knob, Lizzie entered the deserted living-room on stumbling feet.

She was carrying a tray of dishes and food--some cold meat on a platter, a cup and saucer, a roll, a butter pat--and she walked slowly, with terror only one leap behind her and blank darkness ahead.
She had only reached the table and was preparing to deposit her tray and beat a shameful retreat, when a sound behind her made her turn.
The key in the door from the terrace to the alcove had clicked.
Paralyzed with fright she stared and waited, and the next moment a formless thing, a blacker shadow in a world of shadows, passed swiftly in and up the small staircase.
But not only a shadow.