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.

Cast: Jodie Comer, Natasha Little, Stuart Graham, Richard Rankin, Valene Kane, Ariyon Bakare, Nicholas Farrell, Joe Layton, Katherine Rose Morley, Eleanor Wyld, Aneurin Barnard, Alun Raglan, Chipo Chung, Kemi-Bo Jacobs, Charles Babalola