This film is an adaptation of the story of Sisyphus whose fate is for all eternity to push a rock up a mountain; on the top, the rock rolls down again and Sisyphus has to start over. Jess tries to save the lives of her son and friends only to watch them die.
There are two distinct phases to the total cycle denoted by A and B. Events happening in these phases are similar but not identical. By having an A and B phase the audience is fooled into thinking that Jess is altering the cycle when in fact she is simply playing her proper role in the alternate phase. In each phase there are three versions of Jess denoted by 1, 2 and 3. The phase alternates between A and B each time all the minor characters are killed and the tertiary Jess character is thrown overboard. The surviving two Jess characters advance from primary to secondary and secondary to tertiary, respectively and a new primary Jess character boards the ship.
A phase: (Film focuses on A1-Jess)
Once the group is on the Aeolus they read about the story of Sisyphus at which point A2-Jess drops her keys and they are found by the group. The entire group enters the ballroom of the ship where A1-Jess catches a glimpse of A2-Jess. Victor runs after A2-Jess and ends up outside where he is confronted by A2-Jess. A2-Jess accidentally fatally injures Victor. A3-Jess has her character shift and becomes the masked killer.
Gregg and Jess walk away from Sally and Downey and discover the note written in Downey’s blood to go to the theatre. A1-Jess walks away from Gregg and heads for the ballroom.
Sally and Downy are told to go to the theatre by A3-Jess. On their way they see blood trails from where A3-Jess dragged Greg's body out of the theatre. A1-Jess kills Victor in the ballroom after he attacks her. We are tricked into thinking A1-Jess then runs to the theatre but in fact A2-Jess shows up in the theatre. This is because after escaping the theatre unharmed this Jess obtains a knife. This knife is used by tertiary Jess in the next cycle to attack Sally and Downy in the bedroom.
A3-Jess kills Gregg, Sally and Downey in the theatre while A2-Jess flees the theatre and gets the knife. A2-Jess, with the knife, is on the top deck of the ship and is heard running by A1-Jess who is immediately attacked by A3-Jess. A2-Jess has no further role in the A cycle. A1-Jess eventually wins the struggle and throws A3-Jess overboard. The cycle is complete. A1-Jess becomes B2-Jess. A2-Jess becomes B3-Jess.
B phase: (Film focuses on B2-Jess)
B2-Jess resets the skipping record and then sees the new group about to board the Aeolus. In the hallway she drops her keys for the new primary group to hear and runs into the bedroom to see the note to go to the theatre written in Downey's blood. Downey was killed in the theatre in the preceding A phase so this note was made using Downey's blood from the B phase that preceded this B phase.
B2-Jess fatally injures Victor on the deck then goes below deck, scribbles another note “If they board kill them all”, takes a shotgun and loses her locket down the grate. This scene shows the audience that Jess cannot alter the total cycle and is in fact playing her proper role in the B phase of the total cycle.
B2-Jess prevents B1-Jess from killing Victor in the ballroom. B2-Jess then saves Downey and Sally from being killed in the theatre where Gregg is killed. Even though this Jess didn’t witness the theatre slaying in the A phase she is aware of B3-Jess’s location thanks to déjà vu. B3-Jess is grazed in the head by B2-Jess.
B2-Jess gives Downey the shotgun and goes to look for Victor. She returns to the ballroom where his body has been thrown overboard.
B3-Jess tricks Sally and Downey into following her into a bedroom where she attacks them using the knife she obtained as A2-Jess. Sally escapes with a fatal wound to her chest while Downey is killed.
B2-Jess searches for Sally who makes the distressed call to the next primary group. She finds Sally amongst a pile of dead Sallies and gives her the brown jacket.
A3-Jess finds A1-Jess and is thrown overboard after a struggle. When Sally dies the cycle resets. B1-Jess becomes A2-Jess. B2-Jess becomes A3-Jess.
A phase: (Film focuses on A3-Jess)
A3-Jess has a character shift when she realizes that she must kill everyone in order to save them. She goes below deck and writes “Go to the theatre” in Downey’s blood before dragging his body out of the bedroom and throwing him overboard. Next A3-Jess drags Gregg out of the theatre. Victor's body has already been disposed of.
A3-Jess tells Sally and Downey to go to the theatre then leaves to get another shotgun and become the masked killer.
When Gregg offends A1-Jess she leaves him alone and A3-Jess confronts him in a balcony above the theatre where Sally and Downey are waiting. A3-Jess kills Gregg, Sally and Downey in the theatre. A2-Jess flees the theatre and gets the knife which she will use as B3-Jess.
A2-Jess is on the top deck of the ship with the knife and is heard running by A1-Jess who is immediately attacked by A3-Jess. A2-Jess has no further role in the A cycle. A1-Jess drops down one level and grabs an axe. A1-Jess attempts to distract A3-Jess by throwing an object. A3-Jess remembers having done this when she played the part of A1-Jess and cuts her off. A3-Jess ultimately loses the struggle and is thrown overboard where she washes up on shore.
Jess goes home and we find out that the real Jess is abusive towards her son. The real Jess is killed by Sisyphus-Jess. In an attempt to escape the loop she puts the body in her car, takes her son and flees. She hits a seagull and throws its body onto a pile of dead seagulls. She gets back into her car and is involved in a head on collision with a truck. She escapes 'unharmed' and is greeted by a taxi driver. Sisyphus-Jess is in fact already dead and the entire film has taken place inside her constructed punishment.
It is likely that the loop started when real Jess, distracted because she was abusing her son, died in the head on collision along with her son. After dying, real Jess becomes Sisyphus-Jess. The cab driver, playing the role of Hermes, escorts her to the harbor where she will join the next primary group about to board Aeolus.