Narcissa hated that she'd kept this from him for so long; honesty between the two of them was something she'd always insisted firmly upon, even when she might not have wanted to hear the truth about Lucius' whereabouts or the grisly details of his missions. She felt sick over keeping a secret from him, even if it was for his own good. They'd faced everything together, especially in the recent past. Perhaps this could be something they dealt with together, too, though should consequences be acted upon she prayed it would only involve her.
She turned slowly to face him again, though it was not easy. "You have to understand. He'd been given an impossible task that everyone knew he would never be able to fulfill. It was done purposefully, with the expectations he would fail and subsequently be killed for his short comings. I couldn't let that happen, Lucius. Without you here, I had to act myself," she said. "I didn't know what to do. Bella was no help. She thought Draco had been given the highest honor and should be grateful. She thought I should be grateful. I had no one else to turn to except.." She bit her lip and had to look away long enough to keep tears from spilling as she recalled the memory.
"I'd been forbidden to speak of Draco's task to anyone. He said it was punishable by death, but I didn't care. I went to Severus about it. I... begged him for his help." She thought she'd spare him the details of her completely falling apart in Severus' arms. No sense in painting a picture like that. "I convinced him to make an Unbreakable Vow with me, to keep Draco safe, help him, and if for some reason Draco should fail, Severus would step in and see that it was done."
Narcissa chanced meeting Lucius' gaze. "There is nothing I wouldn't do for Draco. I had to keep him safe."