He reached the station, only to discover to his horror that he had missed the last train.

horror 是名词，来自拉丁语 horrere（颤抖），本义是"极度恐惧、震惊"。在句中表示"发现错过末班车时那种极度惊恐的心情"。 horror 常用来形容突然遭遇的强烈恐惧感，比一般的 fear（害怕）程度更深，带有"毛骨悚然"的意味。