I have to be honest, I went into this movie with low expectations. It's one of those movie that you want to know as little as possible going in. The movie, although not actually that scary, is intense and unrelenting. This movie will make you squirm. I haven't cringed in horror and disgust like in "Eli" since I played "Dead Space 2". The movie is incredibly well paced, unpredictable, and well acted. The medical specialists intentions, specifically the mysterious Dr. Horn, stayed unknown for the majority of the movie, making them a creepy and intriguing group. The medical horror is what really makes this movie relatively hard to watch (that's a good thing). The combinations of isolation, creepy characters, mystery, and tension make for a great horror movie. Also, the plot twist near the end is fantastically unpredictable, disturbing, and interesting. Most of the horror in the movie isn't even caused by gore. Similarly to the "Texas Chainsaw Massacre", almost all of the violence is off-screen and is accompanied with gruesome sound effects, leaving it up to your imagination. I would say there were only two real issues I had with this movie.
1. Pacing near the end of the movie. The majority of the movie is well paced, dropping clues on the audience slowly, creating more mystery and tension. However, near the end of the movie, that pacing is shattered, slamming plot after plot point on your head which way a little irritating. Also the movie seemed solid in terms of plot holes. I only noticed one and it was incredibly minor, but the fantastic plot twist ending ripped open over half a dozen plot hole in the movie
2. One annoying trope. This movie contained the always irritating "I-know-something-and-you-don't-believe-me" trope. This made parts of the film incredibly frustrating.
Overall, a mysterious film with an ending that shocked me almost as much as that of the "Sixth Sense". Well paced until the end, good acting, interesting characters, and a great plot. This one should definitely be on your bucket list.