That's... surprisingly easier to answer than Cullen expected, given what he suspects Alistair must have been through, given Alistair's obvious mistrust.

He never stops walking, though he turns his head to say over his shoulder, "Because you're my friend."

Up the stairs. "Because I thought you were dead."

Key in the lock. "Because I'm very glad to find that you're not."

(Nobody tell Cullen that that's a possibility in Milliways.)

He steps into the room and goes straight for the window on the far side, hands going to the buckle of his sword belt. "I'm going to rest my sword against this wall, and then I'll turn around."

It's -- difficult. To do this calmly. But given Alistair's flatness and exhaustion...

Well. It's a good thing Cullen was never one for melodramatic reunion scenes.