Detective Hoffman is deemed hero after he saves a young girl and "escapes" one of Jigsaws game, or do it seems. Special Agent Strahm is suspicious of him after his assistant, Agent Perez dies. While Strahm dives into Hoffman's past, a group of 5 people who all helped burn a building which was supposedly abandoned are put to a series of tests, set up by the Jigsaw Killer.

Charlie Gordon is mentally handicapped and all he wants in life is to be a genius. When he gets picked for experimental surgery it looks like his dream may finally come true. But the surgery has side effects that could could kill Charlie. Can Charlie survive being just plain old "Charlie Gordon" and will his newfound romance survive this test of character?