Ivy Moxam escapes from the cellar which has been her home since she was kidnapped 13 years ago. The police search the house she was held in but find evidence which contradicts her story.
The arrival of a team from Scotland Yard puts Ivy under pressure to relive her ordeal, but her responses raise Merchant's suspicions further. Ivy turns to Tim for support only to suffer a crushing betrayal.
Ivy's attempts to reconnect with her sister are threatened by a mysterious letter that appears to be from Mark White. Carne tries to get Ivy to open up about her captivity. Merchant returns to White's house and makes a shocking discovery.
After her DNA is found in the cellar Ivy is arrested for perverting the course of justice. While being questioned she withdraws completely and it is up to Christina to persuade her daughter to reveal the truth about her abduction.
Ivy is left tied up and gagged after putting her own life at risk in order to save Phoebe. Carne and Merchant try to find a way to ensure her safety but have underestimated Mark White, putting themselves in danger.