Draco knows he owes the Dark Lord. This was made perfectly clear to him, the first time they met. His father was a traitor. Lucius Malfoy had gotten himself imprisoned before he was able to pay off that debt, and now it feel to his son to redeem the family name.
In spite of a little voice in his head insisting that his was not why he had joined the Death Eaters, Draco had agreed immediately, and knelt to receive Voldemort's mark.
But now, he wonders if this is where his true loyalty lies, or if the Serpent and Skull will be the end of the House of Malfoy. He tells himself to ignore such thoughts, so as to not wake up in a cold sweat each morning. Sometimes, he even succeeds.