The story entails the bride of the fictional Lord Robert St. Simon disappearing on the day of their marriage. She attends (and participates in) the wedding, but disappears from the reception.
The events of the wedding day are most perplexing to Lord Robert as it seemed to him that his bride, Miss Hatty Doran of San Francisco, was full of enthusiasm about their impending marriage. St. Simon tells Holmes that he noticed a change in the young lady's mood just after the wedding ceremony. She was uncharacteristically sharp with him. The only obvious happening at the church where the wedding took place that was out of the ordinary was Hatty's little accident: She dropped her wedding bouquet and a gentleman in the front pew picked it up and handed it back to her.