Ash and Tanya are still locked in the cellar with Henrietta, after Professor Knowby locked them in. Ash attempts to shoot Henrietta, but she disappears. She then pulls Tanya behind the stairs and kills her.
Knowby is also killed as he attempts to flee the cabin in his car.
Henrietta mutates, and after a brief scuffle, Ash is able to decapitate her. When Ash emerges from the cellar he finds Ruby and Kelly have arrived as well as Ruby's 1982 version.
Ruby please with her past self to forget about the Necronomicon, but 80's Ruby stabs her with her dagger.
With Ruby's last bit of strength, she takes the Necronomicon and knocks 80's Ruby out. Ruby tells Ash and Kelly that she will by them some time as 80's Ruby regains conciousnes.
As Ash and Kelly reach the car, Ash finds that his missing hand has been restored, much to his delight. Realizing that they have already altered the future, they then hear banging from the trunk of the car, and find that Pablo is alive and well and they drive away.
While in the car, Ash asks Pablo to use the Necronomicon to open a time portal back home, but Pablo declines. Pablo is revealed to actually be Baal in disguise. 80's Ruby then smashes the car window and tosses Ruby's decapitated head into the car. Ash is pulled from the car and knocked out.
Ash awakens back at the cabin, as he notices Ruby's spawn being born.
Baal reveals that while they thought they were sending him back to hell, he actually transferred himself into Pablo before he died. He was then able to hide in Pablo's corpse while they all traveled into the past. Baal tells Ash that they are course correcting, and starting their family over that Ash tore apart.
Ash challenges Baal to a fist fight, but says that Baal isn't allowed to use his powers. Ash sweetens the pot by adding that if he wins, Baal, Ruby and their spawn head back to hell and never return, but if Baal wins, he gets to bring their wrath down upon the earth.
Baal seemingly agrees, and Ruby pretends to read a spell that renders Baal powerless, but during the fight, Baal reveals that he still has his powers. Ash gets the upper hand at first, but is eventually overpowered by Baal.
As Baal is about to end Ash, he is momentarily distracted by a crude remark. Ash uses this opportunity to stab Baal with his own claw. Ruby reveals that she ended up finishing the incantation, rendering Baal powerless.
The cabin goes up in flames as the floor begins to break apart, revealing hell beneath. Ash and Kelly make it out as they watch the cabin burn to the ground, and sending Baal, the spawn and presumably Ruby back to hell.
The following day at a celebratory parade in Ash's honor, 80's Ruby is shown among the crowd, still alive as she walks off.
In a post credits scene, someone stumbles upon the Necronomicon, that was still left among the rubble from the cabin.