Horror and science fiction seem to almost go hand in hand. While there are certainly some horror films that are firmly planted in real world science, most of the time stretching of the laws of nature is required to give us that true frightening feeling. It also tends to let us feel safe, allowing us to explore ideas while being confident that surely, none of this could really ever happen. It's that exploration of ideas and morality that make these movies so much fun.
A lot of people seemed to compare Splice to Species, and as a knee jerk reaction, that is easy to do. Both feature a genetically altered female organism that develops into maturity very quickly and has a certain predatory nature. However, to me, Splice has a lot more in common with the novel Frankenstein as both feature a scientist driven to create a new life form for what they believe will be the good of all mankind. Splice's scientist is a female, and this creates a whole new dynamic to the story as she reacts very differently to her "child" than Dr. Frankenstein did.
I would definitely place this film more in the realm of horror than just science fiction as there are some truly disturbing moments. It won't give you nightmares but it will illicit an emotional reaction from you. If you don't like your movies to leave you feeling a bit disturbed, you may not want to see it. If you like your art to push the boundaries just a bit and make you think about morals and what role they should play in science, however, I think you will enjoy this quite a bit. I recommend not reading further if you plan to watch it, as there will be spoilers from here forward.
Elsa is a brilliant and driven scientist who is working in gene splicing to help synthesize proteins that will help the world. She and her boyfriend Clive have managed to create small blob like organisms who create a protein that helps cattle. The company she works for is interested in creating this protein in mass quantities to make a profit, but Elsa would much rather take her research even further and hopefully make a difference for people around the world. Since she wears the pants in her relationship, she convinces Clive to help her out with this in secret. She also doesn't tell him that she's used her own DNA for the human portion of the creature's genetic code.
They push forward and are ultimately successful, creating an organism that is oddly reminiscent of a human yet has many differences as well. Elsa grows very attached to it and ultimately treats her as if she was her child. It's around this time that we learn Elsa's mother was very cruel and abusive toward her and Elsa is clearly using this opportunity to heal her own troubled past as much as she is trying to make a scientific discovery.
As someone who had a difficult relationship with my mother, I sympathized greatly with Elsa at this point. I think most of us feel that there is something our parents may have done wrong in raising us, and if we ever had children, we would swear to do it differently. But in reality, would we just repeat those mistakes? Elsa refuses to deal with the things her mother did to her as a child, refuses to even speak about them in any kind of detail to Clive. As such, she is pretty much doomed to repeat them. While she originally puts forth a great effort to treat the creature, which she names Dren, with love and care, the more independence Dren shows, the more she is unable to trust her. Instead of allowing her child to grow and giving her a degree of freedom, she tries to control her all the more, returning to treating her more like a lab rat than her baby. Once she severs the emotional connection between Dren and herself, she is able to finally isolate the protein that the company so desperately wants to sell.
Clive, on the other hand, starts off distant with Dren, believing they never should have created her and it was a mistake to allow her to live, but he becomes more and more attached to her as she grows. Too attached. I think, since Dren is made with Elsa's DNA, we're supposed to think he's seeing Elsa within Dren and that is what he is attracted to. Personally the "bond" between the two of them was just plain grossing me out, and why Elsa even kept talking to him at all once she found the two of them together I can't say I understand. Yes, Elsa and Clive both crossed lines in their creation and treatment of her, but I think there's a quantifiable difference between cutting off a creature's tail after it kills something and having sex with said creature. It's gross and considering Dren's maturity level, it's essentially statutory rape.
I've seen online that people claim Clive was under a kind of spell, or perhaps Dren was releasing phermones. Personally, I didn't really get that vibe at all.
The two of them realize that regardless of how they may feel about her, Dren is their responsibility. I think they both feel a degree of relief when they believe her to be dead. Much like Dr. Frankenstein, they were not prepared for the results of their intentions and could not fully handle her. Unfortunately for them, Dren was not actually dead, but simply entering a final evolutionary stage. She has now become male, and exacts her revenge on her creators. It is interesting that now that Dren has changed genders, her treatment of both her "parents" flip flops.. Clive is tortured and killed whereas Elsa is raped. After the way Elsa ultimately treated Dren, it is is as if Dren now feels it is equally important to leave Elsa emotionally violated as well as physically. It is perhaps this violation that gives Elsa the courage to deal the killing blow. As we see in the ending scene, Elsa is now completely emotionally dead inside.
While you could perhaps argue that she has learned nothing from the whole experience, being so willing to allow this new creation to come to term, I think Elsa has learned - she simply no longer cares. If the company truly wishes to use this new child of hers for experiments, she may as well let them. As she says to her boss "what's the worse that could happen?" Certainly nothing much worse than what she has already experienced. Sadly, I think Elsa truly has become her mother by this point.