It's not easy being the sole child of a brood of clones, and Kira on Orphan Black has continuously been in the crosshairs of all the drama that occurs around her mother and her mom's sestras. This stress has taken its toll on Sarah's daughter and in the Season 5 episode, "Beneath Her Heart," Kira has a knife on Orphan Black. Sure, it's only a Swiss Army knife, but Kira's just a child. As Kira has continuously been a pawn in the intense feud between the Neolutionists and the band of clones led by her mother, it's concerning to see her hiding a knife from Mrs. S. While her learning some self-defense wouldn't be a terrible plan, this knife could mean that Kira is becoming violent or that Kira may try to kill Rachel. And even though I don't know exactly why she has a knife on Orphan Black right now, I do know that this brief moment from the June 24 episode will have major consequences for the final season.
After M.K.'s death during the second episode of Season 5, Kira interrupted the usual pattern of an Orphan Black season by choosing not to go into hiding at the behest of her mom. Instead, Kira decided to give Rachel what she wants — and presumably what she wants — by letting the Neolutionist scientists examine her unique biology. Although Kira appears fine with Rachel running tests on her, there seems to be an undercurrent of tension between Kira and Rachel in "Beneath Her Heart" that Kira's knife may be confirmation of.
Maybe Kira is playing with a knife in her room because she just wants to test out her new pet mouse's ability to grow back its skin and fur — which is actually a real thing spiny mice can do, according to an article in Nature by Zoe Cormier (yes, the writer does eerily have the same last name as Delphine). Although experimenting on animals would be creepy and unsettling enough on its own, something tells me that Kira has other plans for that knife that don't involve experimenting on animals.
That's because while Kira is with Rachel earlier in the episode, Kira says that no one thinks she should trust the manipulative clone. And when Rachel asks Kira if she does trust her, Sarah's daughter doesn't give an answer. Although Sarah thinks that Kira resents her, there is a possibility that Kira is actually trying to get close to Rachel to help her mother. Not only could the knife be evidence of that, but in Kira's bio on the BBC America Orphan Black page, it says, "As Neolution and Rachel take a renewed interest in her biology, Kira has plans of her own to secure freedom for herself and her family."
So maybe the knife is part of Kira's plan to "secure freedom." How a Swiss Army knife would help her achieve that is unclear, but perhaps it's time to stop underestimating Kira as simply a child — after all, she has already proven to have some pretty remarkable abilities just like her mom and her aunts.