First, Ilsa's boyfriend(forget his name) bangs Dren. There isn't really a buildup or reason for it. I mean, there is for Dren. She has plenty of reason to like him. But up until that point, the guy was thinking of her as a child. He didn't even think of her as a sexual being. That changes pretty goddamn quick. He knows it's morally wrong, and he even resists for about 10 seconds, but he does it anyway. Yeah, I know Dren has his girlfriend's DNA, but come on. Am I really supposed to believe that just because Dren sort of looks like his girlfriend, he's willing to ignore all the moral implications just to get some quick tail?(see what I did there?) So by that logic, it's OK for him to fuck anyone in Ilsa's immediate family, too. (In fact, Dren is basically Ilsa's daughter, so...yeah.) Everything we've seen about his character so far makes him out as a rational, moral person. This plot twist just doesn't make any goddamn sense, and trust me, it's all down-hill from there. It's just pointless shock and awe. You know, of the "Oh my god, my eyes!" variety.
Next, after some arguing,(oh, I forgot. Ilsa catches him in the act.) the two decide to go back to the farm where they're keeping Dren and kill her. They find her (apparently) already dead. They bury her. Their boss shows up. Suddenly Dren comes back as a dude. No really, Dren arbitrarily changes gender. Yeah, I know. It's because Ginger the Amazing Organic Blob did it too. Frankly, it didn't make any sense when Ginger did it, either. So anyway, Dren goes around killing everyone. Then he rapes Ilsa. Again, there is no fucking reason for it. Dren has no motivation to do this. The only reason it happens is so that A) Audiences will be shocked, and B) Ilsa can become pregnant with Dren2.0 or whatever. Which she does, in an absolutly shameless set up for a cheap sequel.
I find it interesting that MovieBob brings up this other movie, the Human Centipede, as the only other example of sci-fi horror, specifically stating that it was bad because it relied too much on the whole "Oh god my eyes!" factor, because Splice does the same thing pretty goddamn often. And again, I really liked the first two acts, when everyone is still getting along. And I know what you're going to say. "It's not supposed to be happy ending. You're supposed to feel sad that they didn't get along, and that everything turned to shit." Well, I would be able to buy that, but it doesn't change the fact that Dren has no motivation to rape Ilsa, and...fuck it, Ilsa's boyfriend has no motivation to bang Dren. Oh yeah, and of course Ilsa is so fucked up that she's going to keep the baby. Why? Because she's crazy, which happens to be a pretty convenient(read: cheap) form of motivation because it can be twisted to fit whatever the plot requires, and in this case that's a sequel/franchise.
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