When the young american Frederick Winterbourne meets his compatriot Daisy Miller in the garden of a grand hotel in Switzerland, he is struck by her beauty, but slightly unsettled by her open ways and her flirtatiousness. Undeterred by this and by his aunt's disapproval, he invites her to join him in a jaunt to a nearby castle, little suspecting that this is going to set in train a chain of events that promises to be a source of heartache and disappointment for him, and threatens to compromise his own social acceptability.