Strange, returning, relieved Macfarlane’s watch at the side door.  Macfarlane, Ambrose, Giddings, and Pringle lay down on the sofa and on the floor of the library.

Three of them were almost instantly asleep.  Not so Ambrose.  As soon as he saw the half-breed left in sole charge his smoldering suspicions leaped into activity.

“If he’s meditating anything queer this is the time he’ll start it!” he thought.  He took care to choose his position on the floor nearest the door.  He left the door open.

From the outside only occasional sounds came now.  The Indians were busy and silent.  Within the house it was so still that Ambrose could hear Gordon Strange puffing at his pipe.

The half-breed was sitting in the doorway outside, with his chair tipped back against the wall.  By and by Ambrose heard the front legs of the chair drop to the floor, and an instinct of caution bade him close his eyes and breathe deeply like a man asleep.

Sure enough Strange came into the library.  He was taking no pains to be silent.  Stepping over Ambrose he crossed to the mantel, where he fumbled for matches, and striking one made believe to relight his pipe.

Now Ambrose knew that Strange had matches, for when they took John Gaviller up he had seen him light the lamp at the foot of the stairs and return the box to his pocket.

This then must be a reconnoitering expedition.  Ambrose had no doubt that when the match flared up the half-breed took a survey of the sleeping men.

He left the room, and Ambrose heard the chair tipped back against the wall once more.

A little later Ambrose became conscious that Strange was at the library door again, though this time he had not heard him come.

He paused a second and passed away as silently as a ghost—­but whether back to his chair or farther into the house Ambrose could not tell.

Rising swiftly to his hands and knees he stuck his head out of the door.  There was light enough from the outside to reveal the outlines of the chair—­empty.

Without a thought Ambrose turned in the other direction and crept swiftly and softly through the passage into the stair hall.  He did not know what he expected to find.  His heart beat thick and fast.

He scarcely suspected danger to Colina, who was strong and brave.  Was it her father?  Reaching the foot of the stairs he heard a velvet footfall above.

He hastened up on all fours.  The stairs were thickly carpeted.  Gaining the top his strained ears detected the whisper of a sound that suggested the closing of Gaviller’s door.

He knew the room.  It was over the drawing-room, and cut off from the other rooms of the house.  To reach the door one had to pass around the rail of the upper landing.

Arriving at the door he did indeed find it closed.  Under the circumstances he was sure Colina would have left it open.