A few days later, Henry goes to the horse races with Catherine, Helen Ferguson, Crowell Rodgers (the boy who had been wounded by the shrapnel shell), and Mr. Meyers. Meyers is well-connected in the crooked world of Italian horse-racing. At the track, Catherine notices a horse that has been dyed dark-purple, and insists they bet on it because she believes it is a champion horse in disguise. The horse wins, but they win much less than expected because heavy betting just before the race shifted the odds.
Sports and games continue to be important during wartime, but the games are increasingly rigged. This change suggests both the immorality of the war but also that the game of life is rigged—it always ends in death.
They then bet based on a tip from Mr. Meyers and win again, but Catherine soon tires of this. Henry and Catherine leave their friends to be alone together, and Catherine bets on an unknown horse, which loses badly. Nonetheless, she is happier and she and Henry agree that they feel best when alone together.
Catherine would rather lose money on a horse she chose than win by cheating. In a sense, her relationship with Henry is that "unknown horse." She'll do everything to escape the rigged world to live within the privacy of their relationship. Henry joins her, giving up the masculine games he has long enjoyed.