Lucius didn't want to believe him. His sense of pride wounded, his instincts were to deny. He would not be going to Azkaban, and the Dark Lord would certainly find no reason to humiliate the family of one of his most loyal followers. Certainly Draco would make it his pleasure to do the Dark Lord's bidding, as he had been raised to do, and Draco surely knew by now that Lucius would do anything the Dark Lord ordered, barring a few notable exceptions that, he was sure, the Dark Lord knew not to request of him. He wanted to argue, but faced with his son's demeanor, Lucius felt compelled to listen. Surely, if something as drastic as Draco claimed were to happen, it might explain the lack of respect that Draco had been showing him. At the very least, it would explain what had happened to his son. And it would sate his curiosity.
He wanted to take a seat, but in this place, every surface looked suspect. Instead, he rested both hands on top of his cane and waited, for his son to proceed.