There should be another category to describe films that don't exactly fit the accepted genres of horror, supernatural or psychological thriller.<br /><br />I call it the "Puzzle-Box" genre. Puzzle-Box films challenge you to think and discover the answers, rather than spoon-feeding them to you. Not everyone enjoys that when going to the movies. Classifying a film as a Puzzle-Box would make it easier for that film to find its audience.<br /><br />THE I INSIDE is one of those films. Others are MULHOLLAND DRIVE, IDENTITY (same writer as THE I INSIDE), JACOB'S LADDER, and many modern Korean films, such as OLDBOY, HYPNOTIZED, TALE OF TWO SISTERS, and the brilliant but obscure SPIDER FOREST. And to a lesser extent, MEMENTO, which is fun on the first watch, but bored me on the second, since no new clues are revealed.<br /><br />THE I INSIDE give more answers at the end than OLDBOY or MULHOLLAND DRIVE, but it is still a fascinating film.<br /><br />This is is Ryan Phillippe's most challenging role, and he does an excellent job, but the standout for me was Piper Perabo-- she went through some tricky personality quirks (I'm purposely leaving things vague) which added to the mystery.