The lives of the clones will become extra complicated in the next episode of "Orphan Black" season 4.

In the trailer for the episode, titled "Human Raw Material," Krystal Goderitch returns to make it more difficult for Alison and her other clones (Tatiana Maslany).

Series creators John Fawcett and Graeme Manson teased Krystal's return in an interview with Entertainment Weekly.

"Krystal is definitely part of the fun of the next episode, which is really exciting. As is one of the pairings that we have been so enthusiastic about from the beginning of planning season 4, which is putting Cosima with Donnie in a mostly comedic scenario, so that's definitely the fun to look forward to next week," Fawcett said.

The trailer also shows that Sarah and her foster brother Felix (Jordan Gavaris) are fighting, but it is not revealed what they have been arguing about. Gavaris revealed in a recent EW interview that Felix will have a hard time accepting the fact that Sarah has blood connections to their foster mother S (Maria Doyle Kennedy), which makes him the only one who has no family.

"I think he's just grappling with where he fits in, where his place is in the family, and I think it might mean he gets to explore new relationships," the actor said. But he refused to reveal the identity of the person whom Felix will have a new relationship with.

Manson, meanwhile, revealed that there will be more spine-tingling scenes in the next episode of "Orphan Black" season 4. According to the series co-creator, fans will see more disturbing scenes aside from the horrors that they saw during the bot implantation on someone's cheeks. This time, the creepy images will be provided when Alison and Donnie (Kristian Bruun) push through with their IVF treatments.

"Orphan Black" season 4 episode 5 airs on Thursday, May 12, on BBC America.