Sam Reide and his power of the time stream is back. Some time has passed since the death of his girlfriend in "Butterfly Effect 2" and her killer is set for execution on death row. Only now, Sam is convinced that Lonny may not be the killer. Set on freeing the man he thinks is wrongfully imprisoned, he skips back in the time stream once again merely to observe and get an eye witness account of the events of that fateful night. Only this time Sam manages to change the past, which drastically alters the future once again.