As her 40th birthday approaches Emma stops sleeping. She realises she is repeating the same unsettling behaviour as her mother, who had a psychotic break on her own 40th. Is she turning into the very monster she has spent a lifetime trying to forget?

After their mother unexpectedly dies, Emma and Phoebe are shocked to learn her death is suspicious. Reeling from recent events, and with worsening insomnia, Emma is forced to come clean to her husband Robert about her past.

Emma seeks solace in a new friend while Phoebe replaces her sister in the family home. As Emma digs deeper into the past, a forgotten childhood memory shines a light on her relationship with Phoebe, causing her to doubt her sister's intentions.

As Emma comes under the spotlight, she becomes increasingly convinced of her sister's treachery. Before she can get answers to a newly emerging memory, tragedy strikes and Emma begins to mistrust herself.

Realising her home has been infiltrated by a wolf in sheep's clothing, and her family is in danger, Emma races to save them. Can she prevent a shocking vengeance against her family? Or will history repeat itself?