On a June morning in 1923, Clarissa Dalloway, the glittering wife of a Member of Parliament, is preparing for a grand party that evening.

As she walks through London, buying flowers, observing life, her thoughts are in the past, and she remembers the time when she was as young as her own daughter Elizabeth; her romance with Peter Walsh, now recently returned from India; and the friends of her youth. Elsewhere in London, Septimus Smith is being driven mad by shell shock. As the day draws to its end, his world and Clarissa's collide in unexpected ways.