A veil of sadness lies over the oppressively hot summer days. Cleo dives into daydreams with her cousins, the girls share secret signs and rituals. Flowing gently, in impressionistic images, the empty space that the death of Cleo’s sister has left in the family is poetically encircled.

The corpse of a shabbily dressed young woman has been discovered in the mud flats of the Thames at low tide. Police assume she's a prostitute, but Dr. Watson suspects something more and goes to his old friend Holmes, now retired and at very loose ends.