Martin "Wags" Wagner, an aging catcher in the San Francisco Giants farm system, is offered a new assignment—take a promising young pitcher under his wing and show him the ropes. Martin's manager is cagey about the new player, giving only his name, Andrei Dinescu, and his country of origin, Moldova. Despite the mysterious circumstances, Martin accepts the assignment, hoping to earn a return to the big leagues.

After his first bullpen session with the strange new pitcher, Martin is shocked by Andrei's lack of physical ability and his unfamiliarity with the game of baseball. However, with each passing week, Andrei's strength and skill grow exponentially, and his miraculous leaps in both ability and velocity frighten Martin. This fear is compounded by the organization's obvious attempts to keep Andrei separated from the rest of the team.

Wags begins to wonder if maybe he hasn't made a deal with the devil, and if he has, what is it going to cost him?