"Insidious" was quite a ride. With solid direction, good acting and decent writing, "Insidious" plays out as a somewhat respectable part of the recently prolific supernatural subgenre.

The film has a familiar narrative. In the surreal tradition of "The Exorcist" and "The Omen," "Insidious" follows a family with a child-related problem. The family’s young son Dalton has fallen into something resembling a coma, baffling his doctors and leaving his parents distraught. Strange things start happening in the family’s house. Objects move involuntarily, doors mysteriously open and shut, and unsettling occurrences plague the night. It soon appears that something supernatural is at work.

When the house’s haunting climaxes in the form of a phantom intruder, the family opts to move into a new house and put their experiences out of mind. It becomes clear that leaving the troubled house did not solve the family’s problem. The entity has followed them, and it has apparently grown bolder, angrier and scarier. The family has a psychic visit their new house, and she confirms what the audience can already infer: evil forces are influencing young Dalton’s health and his soul is in terrible danger.

The story may sound average and lacking in originality, but "Insidious" does not disappoint. The scares and jumps in the first two acts were genuinely frightening and executed quite well. The writing and acting during this first portion of the film was decent despite its far-fetched subject matter, with Patrick Wilson ("Watchmen") and Rose Byrne ("Get Him to the Greek,") both giving respectable performances as the troubled child’s parents.

The film’s third act was absolutely atrocious in every way possible. The writing stops short, the narrative collapses in on itself, the acting suffers, and the direction and cinematography become unbelievably bad. The revealing of the film’s most foreboding demon is a completely laughable letdown, and the ending left more than a few people groaning in the theater.

What’s noteworthy about "Insidious" is the way it introduces its supernatural elements. The strong first acts derive their strength from the way the writer and director progress the weird events the family experiences from mild to severe, by using various standard horror techniques and devices in such a sequence that forms into an intriguing and frightening film. Moreover, the story’s use of astral projection (the soul leaving the body as one sleeps) as a major plot device moves the film into territory not commonly approached by Hollywood.

All things considered, "Insidious" was enjoyable. It was suspenseful, engaging, and frightening with little yielding. The scares are paced just right, so that the audience never knows when exactly the next one will occur. Insidious lives up to its potential as genre runoff, as a side project of the creative talents behind "Paranormal Activity" and "Saw. To all those seeking something purely original, I’d say move on. To everyone else, "Insidious" is worth seeing.