Orphan Black” Season 5 recently saw the death of one of the Leda clones, all played by Tatiana Maslany.

In “Clutch of Greed,” M.K. helped Sarah escape with her daughter, Kira (Skyler Wexler). In so doing, she pretended to be Rachel. However, Rachel’s former ally, Ferdinand (James Frain), couldn’t be fooled. After seeing M.K.’s scars, he immediately figured out that she’s not Rachel. Even though this was the case, Ferdinand felt the need to get his revenge on Rachel for stealing his money.

Read: What happened to Sarah, Helena and Cosima in “Orphan Black” Season 5, episode 1?

Ferdinand physically hurt M.K. and even let her know that he’s aware she’s not really Rachel. Unfortunately, M.K. could no longer do anything since Ferdinand stomped on her chest several times until she died. The brutal scene was heightened by the crushing sound of M.K.’s bones. And to make things worse, she died while helping Sarah and just before she got into the mix with all of her other Leda sisters.

M.K. was introduced in Season 4, and in 2015, series creators Graeme Manson and John Fawcett announced her upcoming arrival in the hit BBC America series. “Her name is M.K. A mysterious name for a mysterious character,” Manson told Entertainment Weekly.

“We’re excited about this new character because it really has been fun unpacking and unveiling this story of this slightly traumatized clone who has a deep past,” Fawcett explained.

At the time, Manson also revealed that M.K. may be coming out of the shadows, but she’s actually a character that knows more things about her sestras and the Neolution. “Sarah is meeting a clone who has got more answers than she does, and yet she’s a slippery character. And very elusive. And quite highly skilled and very smart. And it is interesting as Sarah tries to interact with this character who is almost kind of like a Deep Throat kind of character,” he said.

Elsewhere in Season 5, episode 2, Helena killed her neonatal doctor for fear that she is a member of the mysterious organization, Neolution. Helena stabbed the physician with a needle through her cheeks and tongue and pinned her to the hospital bed.