There's a quiet sound almost like a sniffle as he nuzzles in all the closer to his mother. Eventually, he nods slightly in agreement, murmuring a soft, "Okay."

It may yet take him some time to properly believe it, but it's a good start. That's all right, because he doesn't need to. What he needs, once his mother lets him go, is to curl up properly into Sirius' arms. Because there Sirius is now, having just made his way into the office. Catching hold of his son feels absolutely necessary and is absolutely welcomed. Lily's got dealing with Dumbledore handled. Sirius can take care of their eldest.

"Don't worry, son," he murmurs into Harry's hair, "Your Mum's got this sorted, nn?"

"Thanks, baba."

And Lily certainly does seem to have it sorted. Dumbledore looks quite briefly taken aback at the woman's vehemence, but doesn't waver just yet in his goal. (He really, really ought to have been in Slytherin.)

"I'm quite aware of the possibility of interpretation," he replies mildly, "But tell me, Lily, how exactly is it that you protecting him is going to result in Voldemort's defeat?"

"Well, how is sending Harry off to be killed going to result in his defeat?" Sirius can't help but shoot back, holding his son a little more protectively against him, "He's fifteen."

There might be a brief flicker of an apology Lily's way for the outburst. He had just told Harry she had it well in hand, but he can't help the flicker of his own protective fury. His attention will turn back to Harry once he's done, though; pressing a firm kiss against the boy's hair.