...
Because he had made certain mistakes, Dumbledore knew that his remaining time was limited.
At the same time, he knew.
Malfoy had joined the Death Eaters and received a mission from Voldemort to kill him.
And yet, both Dumbledore and Voldemort knew perfectly well:
Malfoy could not succeed.
Voldemort simply intended to use Malfoy's failure to punish his parents, who had failed in their own missions.
That's right.
Dumbledore had seen through everything: "When Malfoy fails, the one to carry out the mission in his stead will be you, Snape."
Snape remained silent.
Dumbledore had foreseen Voldemort's eventual capture of the school: "Snape, do you remember your oath to me, that you would do everything in your power to protect the students of Hogwarts?"
Snape nodded with difficulty.
