Assuming those crows aren't obscuring Alucard's sight too much, he may catch a slip of white ghosting along the rooftops in his direction. Assuming it is a little hard to see, he should at least feel the hair-raising tingle of a holy aura closing in, fast, though it's oddly tainted by a vague undercurrent of something... Else. Allen's seen the crows gathering, and while he has no idea who or what they're attacking in such appalling numbers, he's here to make them stop. Instead, it's he who comes to a complete standstill the moment Alucard comes into sight, really comes into sight.

"What on...?" He breathes around the sudden lump in his throat, with the unthinking negligence of the utterly stunned. If Alucard cares enough to seek out the source of his voice, he'll see an English boy crouched on the roof of a squat building nearby, face as bloodless as the sheer white of his cowl. A cogwheeled monocle spins slowly over his left eye, its iris currently a screaming red, and though he's facing Alucard, he's not looking at the other at all, just... Up. Up, up, and further up still into empty air, like he just can't stop himself. He doesn't even blink when stray crows dart across his line of vision.