This is a reasonably entertaining movie with stunning visual effects. It is really a modern day version of a mad scientist movie.
The plot is a little thin. It basically revolves around Kevin Bacon's character, Dr. Sebastian Caine, an egotistical, self absorbed scientific genius who, during the course of his work for the Department of Defense, has managed to render animals to an invisible state and return them to visibility. He does not reveal to the Department of Defense, his financial benefactor, that his work has succeeded. Instead, he ignores protocols and decides that the time has come to take his experimentation to the next level and try it on a human being, himself.
To make a long story short, Caine goes ahead with the human experimentation, only to find that he is unable to replicate the success he had with the laboratory animals and render himself visible again, once rendered invisible. He begins to deteriorate mentally, sinking into an inexplicable and bizarre maniacal state until he is totally out of control.
Moreover, Caine, the acknowledged genius of a scientific assemblage, is aware that he is losing it. Yet, he does nothing to assist in the discovery of what went wrong with the experiment and what could be done to correct the problem. He, instead, inexplicably leaves the solution to the self-acknowledged lesser capabilities of his colleagues. This simply does not compute with the film's portrayal of Caine's inherent character.
Moreover, there is also virtually no explanation for Bacon's rapid descent into apparent madness, where his antics range from naughty and not nice to totally evil and depraved. This is a big hole in the story, and Bacon's character reflects this omission, as the viewer is not moved to feel any compassion for him. The character of Caine is, in essence, just a mechanism used to facilitate a lot of action scenes with great special effects.
Therein lies the rub. Caine, as a character, has no redeeming value or quality. In other words he is no Jekyll and Hyde. He is just Hyde. This is why, I believe the movie has been so panned by most viewers, even though they may not have articulated it as such.
With such great visual effects, I am also surprised that more attention was not paid to production details. A latex mask created for Caine does not appear to have breathing holes for the nostrils. The film also occasionally segues into the absurd. In one scene, the ease with which plastic bags of blood were ripped open with one character's bare hands defied reality. I have a harder time ripping open a plastic bag of carrots. In another scene, Caine's character is torched with a flame thrower over, and over, and over again. Yet, like the energizer bunny, he keeps on going. This was simply not believable. The film is fraught with a number of moments of implausibility.
If you are willing to suspend belief and just sit back and accept the movie at face value, however, one should still be able to reasonably enjoy this movie, as it does, despite the plot holes, have its moments, and the visual effects are dazzling.