Severus almost blocked the intrusion, simply out of habit; it was second nature to guard his mind and repel any interference. He kept his thoughts open, struggle though it was, staring blankly back at Draco. He could feel the direction he was headed, but resisted the impulse to offer up the memory himself. Better to let him come across it on his own.
It was a memory full of very mixed feelings - genuine shock at Draco's actions (he hadn't been able to decide between weakness and bravey), smug satisfaction at the Dark Lord's miscalculation, the relief that had come from his short-lived belief that Dumbledore would now cast aside his ridiculous plan to die on a schedule. They had agreed to keep his own position secret, for the time being, but had agreed on very little else. The argument that had followed had been long and, on Severus's part at least, animated. He had insisted, demanded, begged that Dumbledore simply hide Draco away, find someone to protect him - he would have no chance of going undiscovered, he was a child, obviously frightened and rash. With Draco out of the school, there would be no need for Severus to go through with the charade that Dumbledore had planned - he could go back to his master and explain that the plot had been uncovered, and advise Him to wait.
But Dumbledore had only listened with that infuriatingly knowing expression, and then pointed out that Draco already had someone who was in fact bound to protect him, on pain of death; and had raised his hand and reminded Severus that his own death would come soon enough, in any case, and that it was silly to split hairs about exactly when or how it befell him. One old man, he had said, was hardly a good reason to throw aside decades of hard work. The end of the memory was a little muddled in rage, but that was just as well. Severus had no real desire to let anyone know what he had been in the habit of calling Dumbledore in his lower moments. As with any argument with the Headmaster, it ended in defeat.