"OH!" The Doctor entangled his fingers in his hair, eyes wide, "Oh, how could I be so stupid!?"

He turns to Clara, as if the answer had been here all along. "They want to smoke the people out, yeah? They're using oil as their source. They're trying to stop me - us - from getting them out. The oil wasn't here last night, but it is now! It's so obvious!" He wondered if the dates would change when everything will happen. "It'll be harder to put a fire out when the source is oil."