The film did not receive a positive reception, with one critic calling it a minor improvement over the un-watchable previous sequel.
Sam Reide (Chris Carmack) witnesses a woman being killed, then wakes up in an ice-filled bathtub, his vitals being monitored by his sister Jenna (Rachel Miner). Sam can travel back to any time and location during his lifetime (occupying the body of that time in his life), needing only to concentrate on where and when he wishes to arrive. He has helped the local police capture criminals under the guise of being a psychic. Sam pays his sister Jenna's rent and buys her groceries, as she rarely leaves the apartment and lives in squalor.
Later that night, Elizabeth (Sarah Habel), the sister of Sam's murdered girlfriend Rebecca (Mia Serafino), arrives at Sam's apartment. She believes that the man about to be executed for her sister's murder, Lonnie Flennons (Richard Wilkinson), is innocent, and she offers to pay Sam to find the real murderer. Sam turns her down, but goes to speak with the man who tutored him on time travel, Goldburg (Kevin Yon), who reminds him of the cardinal rules: he's not to alter his own personal past, nor travel in time with his body left unsupervised. When Sam was 15, a house fire claimed Jenna's life, but Sam altered time so that Jenna survives. However, Sam's interference with events resulted in the fire killing his parents instead. After Goldburg's departure, their bartender Vicki (Melissa Jones) seductively offers Sam a seductively-named cocktail; he and Vicki have sex, but upon seeing Rebecca's photo, he cannot continue.
Sam changes his mind and agrees to help Elizabeth out. He tries to help Lonnie without time-traveling, but Lonnie refuses the help, believing Sam to be the culprit. Frustrated, Sam travels back to June 1998. He first runs into a drunk Elizabeth, and tells her to stay in her locked car. He goes into Rebecca's bedroom to find her already dead; meanwhile, Elizabeth is attacked in her car from behind and killed. Sam returns to the present, to learn he no longer owns a car, is renting his couch to a roommate named Paco (Ulysses Hernandez), and no longer works for the police. Instead, he is an obsessed former suspect for Rebecca's murder who has repeatedly asked for the case file. He goes to see Lonnie, who in this present is a wheelchair-bound lawyer. He tells Sam he had driven by, saw Elizabeth and Sam talking, and did not stop. Sam visits Goldburg, who suggests he go back to the scene of the third murder and this time only observe. Sam also visits Jenna, who is significantly better off and living more cleanly; she refuses to help him.
Sam travels back to September 2000 and witnesses the third victim, Anita Barnes (Chantel Giacalone), being attacked, only to learn it is her boyfriend attempting to cater to her rape fetish. He is discovered and her boyfriend's punch sends him back to the present, where now Sam is renting a couch from Paco, who is about to evict him for non-payment. Goldburg is missing, and Lonnie is now the third victim, while Anita remains alive, pepper-spraying Sam in the face after he approaches her in the street.
At her apartment, Jenna tells Sam that Goldburg was about to implicate him in the murders, and furthermore tells him she fears a future Sam is the murderer. Sam complains he is now "too stupid" to fix things; Jenna pinky-swears him to not time-travel anymore. Drunk at the bar, Sam propositions Vicki, who is engaged in this timeline. After Sam leaves, the killer shows up and murders Vicki; her body is found by the police near a car body plant. As Sam left his bar receipt behind, he is hauled in by the police. Jenna extricates him; the police put a tail on him as he leaves. As he leaves, he takes Det. Glenn's (Lynch Travis) evidence notebook, which he uses to look at the scene of the crime and travel back to September 2004, before the bodies were found by the police.
He returns to the present to find himself on Jenna's couch as she leaves for work, reminding him to clean up after himself and have dinner ready for her return; their positions now effectively reversed from the beginning of the film. Sam returns to the auto plant, where the police lie in wait to arrest him. Sam convinces Det. Glenn to release him by telling him how his wife (Andrea Foster) mistook Glenn for M.C. Hammer on their first meeting. Returning home, Sam accidentally inhales some burundanga flowers, sent from Goldburg's greenhouse, and can barely haul himself into the bathtub, before time-traveling back to the abandoned auto plant, where he finds a severely injured Goldburg. Running for help, Sam is felled by a foothold trap.
The killer approaches the trapped Sam, removing his mask as he does so, to reveal that the killer is actually Sam's sister Jenna, who can also time travel. She has an incestuous love for her brother, having killed the women, either because she perceived them as rivals for Sam's affections, or because they were new witnesses, introduced by Sam's rescue attempts. Sam travels back in time to the day of the fire that killed his parents; instead of saving Jenna (Catherine Towne), he traps her in her burning room. He awakes in a new timeline where he has married Elizabeth (not Rebecca), and he, Elizabeth and their daughter Jenna (named after his now-dead sister) (Alexis Sturr) are pulling up to a family barbecue, where he is greeted by his parents and a perfectly healthy Goldburg.
The film closes as Sam's daughter puts her fashion doll on the grill and smiles as it begins to melt.Chris Carmack as Sam Reide
Michael Place as Young Sam
Rachel Miner as Jenna Reide
Catherine Towne as Young Jenna
Melissa Jones as Vicky
Kevin Yon as Harry Goldburg
Lynch Travis as Detective Dan Glenn
Sarah Habel as Elizabeth Brown
Mia Serafino as Rebecca Brown
Hugh Maguire as Detective Jake Nicholas
Richard Wilkinson as Lonnie Flennons
Chantel Giacalone as Anita Barnes
Michael D. Ellison as Anita's Boyfriend
Ulysses Hernandez as Paco
Linda Boston as Landlady
Emily Sutton-Smith as Mother in the Park
Dennis North as Sam's Father
Trevor Callaghan as Son in the Park
Peter Malota as Assailant in the Park
Sonya Ayakian as Secretary
Alexis Sturr as Sam's Daughter
Andrea Foster as Glenn's Wife
Daniel Spink as Prison Guard
The movie was filmed in Michigan and concluded filming in October 2008. It debuted as part of the lineup for After Dark Horrorfest III, a horror film festival held in January 2009. The film was released on DVD on March 31, 2009.
Reel Film Reviews characterized the 3rd installment as "A very mild improvement over the nigh unwatchable Butterfly Effect 2."