By connecting stocks through common active mutual fund ownership, we forecast cross-sectional variation in return covariance, controlling for similarity in style (in- dustry, size, value, and momentum), the extent of common analyst coverage, and other pair characteristics. We argue this covariance is due to contagion based on re- turn decomposition evidence, cross-sectional heterogeneity in the extent of the e¤ect, and the magnitude of average abnormal returns to a cross-stock reversal trading strat- egy exploiting information in these connections. We show that the typical long/short hedge fund covaries negatively with this strategy suggesting that hedge funds may potentially exacerbate the price dislocation we document.