This document describes research on the Connected Scatterplot (CS) technique for visually presenting paired time series data. The CS uses dots connected by lines and arrows to show the relationship between two time-varying datasets over time. User studies found that the CS was generally understandable but performed better with explicit labels about the axes and flow of time. It was also better at depicting changing patterns than the traditional Dual-Axis Line Chart, but had limitations for extremely complex data patterns. Guidelines are provided for designing effective CS visualizations.