Two sisters. An intense bond. A bitter rivalry.

Margo is a solitary live-in nanny for an upper-class Kensingon family. Cora is a promiscuous dancer on the cusp of a big break, living hand-to-mouth in a run-down London flat.

Different though they are, an unspeakable incident from childhood haunts them both. When the terrible secret comes to light, their fragile existences shatter, pitting them against each other in a race for survival.

But can there be a winner when a secret is so dark?