The Frenchman saw him coming.
He slipped into the room where the old detective lay.
Raising his finger to his wife, he hissed:
"Hush! He coming up ze stair! Put out ze light—hurry!"
Keeping the door open on a crack when darkness fell upon the room, he peered out and listened intently.
It was too dark to see anything.
But he heard the young detective's soft footfalls passing the door and he stepped out into the hall behind Harry.
Slight as the noise was which he made, the boy heard him and turned around, striving to pierce the gloom with his sight.
La Croix had the boy located.
He suddenly sprang forward with both hands extended, struck against the boy, clutched him by the throat and knocked him over backward.