“Don’t be stupid, Wormtail. The Dark Lord has his ways of knowing. Unless you want to end up where Mason was supposed to end up, you better speak. And now.”

She raised her wand, and "Wormtail" inadvertently took a step back. Which was, of course, of no real use, since all that he could achieve by putting distance between himself and her wand was.... nothing.

Jenna White rolled her eyes at his action, lowering the wand. “Stop it, Wormtail. You know I’m not going to hurt you.”

Peter Pettigrew hesitated. Behind him, the wall stretched like a never-ending boulder – He could not even back away, now. “I can’t kill,” he said, his voice squeaky. “He – he knows it. The Dark Lord knows it. I’m –”

“– too much of a scared-y pants,” Jenna completed the sentence for him. “Wormtail – oh for, God’s sake, get a grip. Stop shivering!”

As if pulled taut by an invisible string, Wormtail's frame stopped trembling at once. His face was still pale, though and, inwardly, he was still aquiver. How could he have even thought he could get away with this? When the Dark Lord told you to kill, you killed.

He had, indeed, been foolish to think that he could only pretend he had killed Roger Mason - and get away with it.