As Alison is terrified by Neolution threats made against Donnie, Sarah and Mrs. S question her loyalty to her sisters. While Sarah is distracted, Siobhan sneaks out to seek vengeance. Meanwhile, Cosima and Susan Duncan work together in a final attempt to discover a cure.

• Renée St. Cyr
• Graeme Manson
• John Fawcett

• Roger Cross
• Stephen McHattie
• Patton Oswalt