A sword was aimed at his heart.

There was a blinding flash, a detonation, and the man who held it staggered back.
The Countess, the last pistol almost touching the man's body, had pulled the trigger.

Marteau seized the sword of the man who had menaced him.

The next instant the chateau was shaken by a terrific roar.

The Russians outside having constructed a rude bomb had blown up the door.
For a second the combat ceased.