"Mr. Cole is the priority, then we worry about the core," Jones tells her team in tonight's episode. She's speaking of the tracer signal: Staying locked on Cole, tracking him in time and space, is the single most important task. All future missions rely upon calling him back, and that need eclipses all others, including the need to preserve the machinery. But it functions as a metaphor for the show as well. Stay locked on Cole and the story stays strong. Lose sight of him and it falters. The characters and emotional arcs of 12 Monkeys have stumbled over its eight episodes, but the story mechanics stayed strong. The show has clearly conveyed the potentially confusing jumps through time and space with seemingly effortless focus, and kept the larger narrative free of distractions by keeping everything centered tightly around James Cole. Until tonight. "Yesterday" inverts most of the expectations the series has established, not entirely successfully. Cole spends his scant minutes of the episode in a dark cellar while his compatriots from 2043 leave their shadowy time-travel bunker for the sunny, spacious halls of Spearhead, a longstanding post-plague institute searching for a cure to the constantly mutating virus. Years ago, Col. Foster (Xander Berkeley) staged a coup, assassinating the world's military and political leaders when they proposed to abandon medical research in favor of retreating to isolation. His teams have harvested every hard drive, server, and processor within 500 miles, building a vast network with one goal: to find a cure for the plague. With Jones' help, he says, they can be one year from engineering a vaccine capable of predicting viral shifts before they occur.