He did not stop to think of what he was doing.  With infinite slow patience he turned the knob with one hand, holding his electric torch ready in the other.

When the door parted he flashed the light on the spot where he knew the bed stood.  The picture vividly revealed in the little circle of light realized his unacknowledged fears.

He saw Strange kneeling on the bed, his face hideously distorted, his two hands at the old man’s throat.

Strange yelped once in mingled terror and rage like an animal surprised—­and with the quickness of an animal sprang at Ambrose.

The two men went down with a crash athwart the sill, and the door slammed back against the wall.  There was a desperate struggle on the floor.

Strange was nerved with the strength of a madman.  He could not have seen who it was that surprised him, but in that frantic embrace he learned.

“It’s you, is it?” he snarled.  “I’ve got you now!”

Forthwith he began to shout lustily for help.  “Macfarlane!  Giddings!”

Colina was already out of her room.  She did not scream.  The three men were on the stairs.

“Bring a light!” gasped both the struggling men.

It was Colina who lit a lamp and carried it out into the hall with a steady hand.  Ambrose was seen to be uppermost.  Recognizing the two men her face darkened with anger.

“What does this mean?” she cried.  “Get up instantly!”

Ambrose wrenched himself free and stood up.

“Don’t let him escape!” cried Strange.

Ambrose laughed a single note.

“He tried to kill your father!” panted Strange.  “I arrived in the nick of time!”

Ambrose gasped and fell back in astonishment.  Such stupendous effrontery was beyond the scope of his imagination.

“It’s a lie!” he cried.  “It was I who discovered him in the act of strangling your father!”

Then for the first Colina swayed.  “Oh, God!” she murmured, “have we all gone mad!”

Macfarlane seized the lamp from her failing hand.  Colina ran unevenly into her father’s room.  They heard her cry out within.  Giddings ran to her aid.  He made a light in the room and closed the door.  The little parson moaned and wrung his hands.

Macfarlane had drawn his revolver.  “If you make a move I’ll shoot you down!” he said to Ambrose—­thus making it clear whose story he believed.

“You can put it up,” said Ambrose coolly.  “I’m going to see this thing through.”

Strange had got his grip again.  His smoothness was largely restored.  He actually laughed.  “He’s a cool hand!” he said.

“You damned black villain!” said Ambrose softly.  “I know you now.  And you know that I know you!”

It did not improve Ambrose’s case to say it, but he felt better.  The half-breed changed color and edged behind Macfarlane’s gun.

Colina presently reappeared, showing a white and stony face.  “Mr. Pringle,” she said, “go down and lock the side door and bring me the key.  The rest of you go to the library and wait for me.”