The LEDA clones (Tatiana Maslany) are becoming more desperate to protect themselves from their enemies. This has made them forge alliances with their rivals in the penultimate episode of "Orphan Black" season 4.

Based on the trailer for the upcoming episode called "The Mitigation of Competition," Sarah will find herself working with Rachel despite their past differences in order to go after their new mutual enemy, Evie Cho (Jessalyn Wanlim) and the new HBIC. In the clip, Sarah will go with her foster brother Felix (Jordan Gavaris) to meet up with Rachel despite being still unconvinced if working with Rachel is a good idea.

Cosima and Susan Duncan (Rosemary Dunsmore) will also work together to find a cure to the disease that affects the clones. However, the two will continue to clash with each other because they will have a hard time agreeing with each other's methods.

The sneak peek also showed that Helena will finally return in the upcoming episode. But her arrival will shock Felix, since the pregnant LEDA clone was missing for quite a while.

The threats in the lives of the sestras will continue. In the latter part of the trailer, Alison will discover that someone broke into their basement and tied and gagged Donnie (Kristian Bruun).

The official synopsis for the upcoming episode reads:

"With Susan Duncan deposed, Sarah finds herself in the same position as Rachel — under the heel of a new HBIC — causing the archenemies to come together for the greater good. Cosima and Susan butt heads on the ethical implications of human experiments. Meanwhile, when the Hendrixes' legal counsel, Adele, further investigates Donnie's case, she begins to suspect Felix is keeping deep secrets. Helena's arrival forces Felix to make a difficult decision."

The ninth episode of "Orphan Black" season 4 is slated to air on Thursday, June 9, on BBC America.