Determined to reintegrate, witch Sarah Fenn returns to Sanctuary but a horrific magical murder forces her to work with DI Maggie Knight in solving the case; Harper meets an intriguing stranger on her journey and makes an new discovery.

Following the discovery of a sigil at the crime scene, Sarah and Maggie determine that they have to dig deeper into the killer's identity; having discovered that Lachlan's identify, Harper grapples with her feelings towards him.

Sarah and Maggie determine that Angela has the most to gain from the murder and agree that they need more evidence; a magical attack on Harper forces Sarah to betray Maggie; following the attack, Sarah rekindles her romance with Lachlan.

Lachlan is arrested for Pierre's murder; Sarah and Maggie fight to clear his name by revealing Ryan's magical death to Deveraux; Angela intensifies her campaign against witches; Harper, revealing her magic, unbinds Lachlan.

Having unbound Lachlan, Harper fears she might have damaged his magic forever; fearful of the ramifications, Sarah hands over Starcross to the Moot; when Bea goes missing, the killer's identify is revealed; Sarah and Harper fight to save her life.

Sarah, Lachlan, and Harper plan to leave Sanctuary; Maggie discovers Lachlan's connection with the revolutionary Redhaven group; Angela's anti-witch bill passes but the truth about Luka is revealed; Sarah and Harper both embrace their destinies.