Suddenly, the grin was wiped from his face, and he was tense from head to foot.

Standish, on his way homeward, was strolling past a clump of dwarf shrubbery.  And, idly watching him, Gavin could have sworn that one end of the shrubbery moved.

Then, he was no longer in doubt.  The bit of darkness detached itself from the rest of the shrubbery, as Milo lounged past, and it sprang, catlike, at the unsuspecting man’s back.

Into the path of light it leaped.  In the same atom of time, Gavin Brice shouted aloud in sharp warning, and dashed forward, the collie at his side.

But he was fifty feet away.  And his shout served only to make Standish halt, staring about him.

It was then that the creature from the shrubbery made his spring.  He struck venomously at Standish, from behind.  And Gavin could see, in the striking hand, a glitter of steel.

Standish—­warned perhaps by sound, perhaps by instinct—­wheeled half-way around.  Thus the knifeblow missed its mark between his shoulder-blades.  Not the blade, but the fist which gripped it, smote full on Standish’s shoulder.  The deflected point merely shore the white coat from neck to waist.

There was no scope to strike again.  And the assailant contented himself with passing his free arm garrotingly around Standish’s neck, from behind, and leaping upward, bringing his knees into the small of the victim’s back.

Here evidently was no amateur slayer.  For, even as the knife-thrust missed its mark, he had resorted to the second ruse, and before Standish could turn around far enough to avert it.

Down went the big man, under the strangle-hold and knee-purchase.  With a crash that knocked the breath out of him and dazed him, he landed on his back, his head smiting the sward with a resounding thwack.

His adversary, once more, wasted not a jot of time.  As Standish struck ground, the man was upon him, knife again aloft, poised above the helpless Milo’s throat.

And it was then that Gavin Brice’s flying feet brought him to the scene.

As he ran he had heard a door open.  And he knew his warning shout had reached the ears of some one in the house,—­perhaps of Claire.  But he had no time nor thought for anything, just then, except the stark need of reaching Milo Standish before the knife could strike.

He launched himself, after the fashion of a football tackle, straight for the descending arm.  And, for a few seconds all three men rolled and wallowed and fought in a jumble of flying arms and legs and heads.

Brice had been lucky enough or dextrous enough to catch the knife-wielder’s wrist and to wrench it far to one side, as it whizzed downward.  With his other hand he had groped for the slayer’s throat.

Then, he found himself attacked with a maniac fury by the man whose murderous purpose he had thwarted.  Still gripping the knife-wrist, he was sore put to it to fend off an avalanche of blows from the other arm and of kicks from both of the assailant’s deftly plied feet.