Season 4 of the drama will see leader-of-the-pack, Sarah, reluctantly return home from her Icelandic hideout to track down an elusive and mysterious ally tied to the clone who started it all - Beth Childs. Sarah will follow Beth’s footsteps into a dangerous relationship with a potent new enemy, heading in a horrifying new direction. Under constant pressure to protect the sisterhood and keep everyone safe, Sarah's old habits begin to resurface. As the close-knit sisters are pulled in disparate directions, Sarah finds herself estranged from the loving relationships that changed her for the better.

• Tatiana Maslany
• Jordan Gavaris
• Josh Vokey
• Maria Doyle Kennedy
• Ari Millen
• Kevin Hanchard
• Kristian Bruun