I mean why would a doctor/school teacher put himself in so much danger by abducting an alien from the military, just so he can do his own private research on her, in order to be able to breed a new super-race that's immune of all deceases. It's a quite ridicules one that makes less and less sense, the more you start to think about it. Sunny Mabrey is a boring alien, who certainly isn't being seductive enough, even though that's basically the only point of her entire character. It's simply below par and besides most actors seem to be miscast in their roles. The acting is really one of the biggest problems of this movie.
On the other hand it's lacking the characters and certainly the fine actors of the previous 2 Species movies. The alien is a female again and the movie features less of Natasha Henstridge, who added very little to the previous sequel. It's the second sequel in the Species-series and even though they have learned from their mistakes from the previous Species sequel, it still isn't a better movie.
Besides, the fact that the two halves of the movie differ so much from each other and don't quite connect well enough, don't make the movie any better. Not that either halve of the movie impresses much though. Abbot's 'brilliant' research, while its second halve is more about Dean and its action and science-fiction elements. This movie can be divided in different parts.