While mapping an unexplored valley, Roxton is surprised by a terrified young woman, who after uttering an enigmatic warning, dies in Marguerite's arms. Roxton, Marguerite, and Malone head toward an ominous castle when a sudden rainstorm forces them to seek shelter. There, under a mysterious influence, the three are led to separate rooms where they each find opulent evening wear of the same vintage as that worn by the young woman. Marguerite and the two men begin to take on new personalities, eerily re-enacting a romantic triangle of intrigue, with Marguerite playing Roxton against Malone as both men compete for her attention. Meanwhile Challenger and Veronica similarly find themselves at the castle, where they are welcomed by Roxton, Marguerite, and Malone, all strangely possessed by the spirit-wearers.