In both developed and emerging stock markets, overnight (close-to-open) returns are higher relative to intraday (open-to-close) returns. We provide a noise trader-based explanation for this “overnight-intraday return gap.” We start by developing a cross-sectional asset pricing model with a systematic noise trader risk. Then, we use exact and exhaustive retail investor trade flow data available for the Korean stock market to establish the relationship between the overnight-intraday return gap and retail flows. Furthermore, we use the pandemicinduced retail trading frenzy as a shock to retail trading intensity to address endogeneity concerns.