Maybe they should have knocked. The plan was, after all, to start with diplomacy and if, and only if, that broke down, to start shooting. Breaking into someone's house wasn't entirely diplomatic, but it wasn't like the vampires locked the door or anything. Not out of a kind of Canadian trust and camaraderie, but, Sitwell suspected, because it was the middle of the tundra and nobody with any sense was going to stroll into a coven, and that worked for them. Just like going on living and not expecting to be attacked by vampires should have been working for the people of Northern Alaska, hence the visit to discuss this break in habit and regulation.
"They're probably very nice," Sitwell mused hopefully, not really sincerely, because they were here to discuss a cannibalism problem and those sorts didn't have much hope. Still, it helped him stroll along ahead casually at Coulson's instruction, one hand on his gun and letting Coulson keep them illuminated. It didn't get any warmer the deeper they went, or any brighter, and Sitwell was starting to think they'd broken into the wrong castle when he finally heard it.
A faint crackling, and a quiet but distinct pop, like a bowl of Rice Krispies. "Hello?" he tried tentatively. "My name is Agent Sitwell, I'm with the Strategic Homeland-- woah." There wasn't a 'woah' or even a 'W' in S.H.I.E.L.D., but Sitwell had pushed open a door that led to a staircase flooded with an eerie, shifting light, like somewhere at the bottom there was a ginormous lava lamp. The crackling sound got louder, fizzing now that he could hear it. "Excuse me?" he tried again, and offered the delayed but deserved courtesy of knocking on this door.