Along with Krystal's come back, Sarah and Ferdinand are set to join form an alliance in "Orphan Black" season 4 episode 5.

"Orphan Black" season 4 episode 5 is entitled "Human Raw Material." As per series co-creator John Fawcett, the episode is set to see a unity between Sarah and Ferdinand. In his interview with Entertainment Weekly, he said that Sarah and Ferdinand had had a kind of relationship of being frenemies, since the start.

According to Fawcett, Ferdinand was not exactly someone that people could completely trust, but it appeared that M.K. was not as well. For the co-creator, that was the sort of what the "Orphan Black" realm was like, which he described as "very grey allegiances" and hanging oneself out for people that he was not sure whether he could trust or not.

For Fawcett, both of the characters, moving forward, played into later parts of the season; thus, it was just a little building towards something larger.

In the same interview, Fawcett also revealed the return of Krystal in "Orphan Black" season 4. According to the co-creator, Krystal was definitely part of the fun of the next episode, which was really exciting. Cosima and Donnie were also put in mostly comedic situations, which contribute to the humor fans could look forward to.

In the promo trailer, Krystal as seen as she stitches matters, along with the complex situation of the other sestra clones. With her return, her overall impact to the "Orphan Black" story arc is yet to be revealed.

"Orphan Black" season 4 episode 5, "Human Raw Material," is set to air on May 12 on BBC. Watch the promo clip here.