Serge looked at the brothers.

“Tell me,” he said.  “I do not understand.”

Halfoff turned a moment from his work and looked at Serge.

“Brother,” he said, “will you give your life?”

“Is it for Olga?” asked Serge.

“It is for her.”

“I give it gladly,” said Serge.

“Listen then,” said Halfoff.  “Our sister is condemned for the killing of Popoff, inspector of police.  She is in the prison of the condemned, the house of the dead, across the street.  Her cell is there beside us.  There is only a wall between.  Look—­”

Halfoff as he spoke threw aside a curtain that hung across the end of the room.  Serge looked into blackness.  It was a tunnel.

“It leads to the wall of her cell,” said Halfoff.  “We are close against the wall but we cannot shatter it.  We are working to make a bomb.  No bomb that we can make is hard enough.  We can only try once.  If it fails the noise would ruin us.  There is no second chance.  We try our bombs in the crucible.  They crumble.  They have no strength.  We are ignorant.  We are only learning.  We studied it in the books, the forbidden books.  It took a month to learn to set the wires to fire the bomb.  The tunnel was there.  We did not have to dig it.  It was for my father, Vangorod Vasselitch.  He would not let them use it.  He tapped a message through the wall, ‘Keep it for a greater need.’  Now it is his daughter that is there.”

Halfoff paused.  He was panting and his chest heaved.  There was perspiration on his face and his black hair was wet.

“Courage, little brother,” said Kwitoff.  “She shall not die.”

“Listen,” went on Halfoff.  “The bomb is made.  It is there beside the crucible.  It has power in it to shatter the prison.  But the wires are wrong.  They do not work.  There is no current in them.  Something is wrong.  We cannot explode the bomb.”

“Courage, courage,” said Kwitoff, and his hands were busy among the wires before him.  “I am working still.”

Serge looked at the brothers.

“Is that the bomb?” he said, pointing at a great ball of metal that lay beside the crucible.

“It is,” said Halfoff.

“And the little fuse that is in the side of it fires it?  And the current from the wires lights the fuse?”

“Yes,” said Halfoff.

The two brothers looked at Serge, for there was a meaning in his voice and a strange look upon his face.

“If the bomb is placed against the wall and if the fuse is lighted it would explode.”

“Yes,” said Halfoff despairingly, “but how?  The fuse is instantaneous.  Without the wires we cannot light it.  It would be death.”

Serge took the bomb in his hand.  His face was pale.

“Let it be so!” he said.  “I will give my life for hers.”

He lifted the bomb in his hand.  “I will go through the tunnel and hold the bomb against the wall and fire it,” he said.  “Halfoff, light me the candle in the flame.  Be ready when the wall falls.”