"I'll forego technical terms and translate into realities you can grasp. It amounts to this: The bartender poured the actual poison into the glass, but all unknowing. However, as a dominant factor of the equation he must be further developed along the lines of secondary motivation. In other words, a completely unrelated motivation on his part cleared the way for the crime."
Dalrymple's fingers were flying. More of the weird symbols were appearing. "The motivation for the weight he bears in the case is made up of two characteristics—habit and greed."
"And where does that get us?" I asked.
"It reveals the fact that the bartender poured the poison into the bottle. But without knowledge that it was poison nor with malicious intent."
"That's impossible!" I said.
"Not at all. The whole sequence becomes clear when we strive to complete our equational balance in the first phase. The bartender poured an unconsumed drink back into the bottle after whoever ordered it walked out without drinking it."
Of course! The logic of it hit Donovan and me at the same moment. Donovan said, "How in the hell did you ever think of that?"
He meant it as a compliment but Dalrymple did not take it as such. "I didn't think of it, you fool. I worked it out. Haven't you understood anything I've told you? It's all here in the progression of the equation. Incidentally, that factor is the pivot of the whole sequence. Your stupid logic should carry you on from there."
"Somebody was trying to poison somebody else!" Donovan said.
"There had to be two men," I added. "They came in and ordered drinks. One poured poison in the other's drink. Then they left without—"