In this chapter we explore the effect of the ball/strike count on the behavior of players and umpires and on the final outcome of a plate appearance. We use Retrosheet data from the 2016 season to estimate how the ball/strike count affects the run expectancy. We also use PITCHf/x data to explore how one pitcher modifies his pitch selection, how one batter alters his swing zone, and how umpires judge pitches based on the count. Along the way, we introduce functions for string manipulation that are useful for managing the pitch sequences from the Retrosheet play-by-play files. Level plots and contour plots, created with the use of the ggplot2 package, will be used for the explorations of batters’ swing tendencies and umpires’ strike zones.