Grace was a child when Legion initiated Judgment Day. She witnessed various tragedies, starting with witnessing a plane crashing onto the ground. Her father was killed by other survivors over a can of peaches. Years later, she was attacked by another group of rogue survivors, but she was saved by Dani Ramos, who told those attackers that preying upon other survivors was what Legion wanted, which would make the human race become extinct much quicker. Convinced, these survivors decided to join Dani's Resistance to fight against Legion. Since then, Grace had stayed with Dani, while Dani raised Grace like her own daughter.
At a certain point, Dani was wounded during a battle. Grace, along with the squad led by William Hadrell, escorted Dani back to base on Dragonfly 3. After landing, the transport was destroyed by the enemy force, and the Resistance soldiers began to fight multiple Rev-7 units. Grace was ordered by Hardrell to bring Dani back to base. However, Grace was seriously wounded while protecting Dani, but she succeeded in her mission. After she was brought back into the base, Grace volunteered to become Augmented.
In 2042, Grace and her unit captured a TD Chamber, neutralizing every unit within the chamber. However, they found that a Rev-9 had been sent back in time to 2020 to kill the younger Dani. Grace volunteered for the time travel mission to 2020 to protect the younger Dani, while Dani was reluctant but granted her request after Grace's begging.
After Grace arrived naked in Mexico in 2020, she was helped by a couple before she attacked policemen, who tried to take her from the scene. Grace then took clothes from the man who helped her and left the place with the couple's car.
She managed to find the young Dani Ramos and her brother Diego Ramos in the factory where they worked. She rescued them from Rev-9. However, after a car chased, Diego was killed by the machine. Sarah Connor arrived at the scene and saved them, only to find that her car was stolen by Grace to take Dani away. They were reacquired by Sarah outside a drug store after Grace crashed due to the intense battle with the Rev-9.
She was unwilling but agreed with Sarah's volunteer to help Dani. After learning the location, where the mysterious texts sent to Sarah were from, was the same with the coordinate tattooed on her belly, they decided to travel to Texas in United States with the help from Felipe Gandal and his son Flacco, only to be attacked by the Rev-9 with a UAV drone before being arrested by the United States Border Patrol. After escaping the detention center, they arrived the coordinate, only to found it was the home to Carl, a CSM-101 Infiltrator, who was responsible for the death of John Connor, Sarah's son.
Carl agreed to help the women as he believed in fate, considering Sarah's action to destroy Skynet had set him free. After acquired two EMP generators from Major Dean, they were attacked by the Rev-9. With Dean's help, they managed to board a C-5 cargo plane after the Rev-9's pursuit and attack, which destroyed the EMP generators.
They were attacked again when being attacked by the Rev-9 in its hijacked aerial refueling aircraft. After the battle, they escaped the plane in a Humvee and landed in a hydroelectric dam. After regrouped with Carl, Dani called the ground as their kill box against the Rev-9.
In the ensuing battle, both Grace and Carl sacrificed themselves to successfully destroy the Rev-9 in the dam.
Dark Fate timeline
After destroying the Rev-9, Dani Ramos and Sarah Connor travelled to see young Grace, who was in a playground with her younger brother and their parents. Before leaving, Dani vowed to protect Grace in the current timeline and Sarah told her that she had to be ready for the coming new Judgment Day and Future War ahead.
- Main article: Augment
Because of her enhancements, Grace has increased speed and strength and combat skills. She is able to fight hand-to-hand with the Rev-9 Terminator and block crushing blows that would otherwise severely injure or kill a normal human soldier.
Grace's augmentation comes with limitations; she is only able to fight at extreme combat levels for brief periods before her energy stores are drained. She quickly becomes weak and unable to fight until she is able to eat, drink water or intake certain medications like insulin.
- Enhanced Human-Cyber Physiology: Grace managed to become a human cyber hybrid through successful surgery. As a result, she ended up gaining similar skills as a terminator with a scale of strength and endurance greater than that of an ordinary human. This made her a perfect candidate to save Dani Ramos from the clutches of Rev-9. Below is a list of what she can do:
- Superhuman strength (limited): Grace exhibits a high domain of strength that rises to normal people, managing to do great things with little or no effort. She managed to lift Rev-9 and throw it against a belt at Dani's factory without any effort. Later, Grace managed to carry out a series of bar throws against the truck that the terminator was driving without major problems. In the battle at the hydroelectric plant, Grace managed to push Rev-9 with the help of Carl against a rotating crusher, overloading her cyber extensions from her arms in the process. In her weakened state, her strength is diminished as seen when she failed to open a steel plant door.
- Superhuman agility: Grace manages to predict a blow before he hits it, making her dodge with great agility. She proved to be able to be extremely agile in protecting herself from the multiple attacks of the terminator, protecting herself only with a car hood in the factory fight. Later, Grace managed to deflect a steel bar against it with extreme ease. She is so quick that she can slice a fly in half.
- Superhuman durability (limited): Grace has proven to be extremely resistant to the powerful blows of Rev-9, one of which is pushing her violently against various equipment in the factory. However, its durability is not eternal. When she overloads herself, her strength and resistance drop, forcing Grace to inject medicine into her veins to replenish herself. Even in a weak state, Grace managed to survive the crusher's explosion against Rev-9, showing only a few scratches and average injuries.
- Enhanced Vision: Grace has a Head-up display ( 'HUD' ) that offers data transparently through visual means, similar to what terminators use. She uses this during the chase of Rev-9, where she aims at her target with various forms of display spread across her visual field to hit him with a steel bar.
- Cyber Access: She was able to access Dani's cell phone network just by touching the electrical circuit directly.
- Master combatant: Grace has shown herself to be quite capable and skilled in protecting Dani from the deadly attacks of her killer. She proved to be an excellent combatant when handling a hammer and trying to damage Rev-9 severely. In the final battle, she managed to dodge all of his blows and retaliate before being hit in the chest by one of his blades.
- Grace's surname "Harper" is not revealed in the film Terminator: Dark Fate, but it is referred by the director Tim Miller during the global premiere of the film.
- In an early concept art of Terminator: Dark Fate, there is a Resistance soldier named Harper. It is unknown if the character later developed into Grace, or he has any relationship with Grace.
- There are two alternate endings for Terminator: Dark Fate with one including Grace's grave, while another features Sarah and Dani sending off Grace's body in a manner of Viking funeral.
- Grace appears in Gears 5 as part of the Terminator: Dark Fate Character Pack 2 DLC along with Rev-9.
Behind the Scenes
- Grace is portrayed by Mackenzie Davis in the 2019 film Terminator: Dark Fate. Stephanie Gil portrays the younger version of Grace in the film.
- Grace is officially described as a "soldier-assassin".  
- Terminator Dark Fate Spoilers: Questions Explained By Director
- Future war flashback - Dani sending back Grace - Terminator: Dark Fate deleted scene
- Terminator: Dark Fate - Deleted Scenes 6 - YouTube
- Terminator: Dark Fate Global Premiere - Part 1 - YouTube
- Dark Fate's Tim Miller Helps Us Answer All Your Burning Terminator Questions | Gizmodo Australia
- Hope Of The Future - Terminator: Dark Fate alternate scenes - Alternate endings
- Terminator Reboot Taps Mackenzie Davis to Star | Hollywood Reporter
- Terminator 6 Lines Up Mackenzie Davis to Play a Soldier-Assassin | Screen Rant
- We’re Close To Having Mackenzie Davis In Terminator Reboot
- Terminator: Dark Fate - Deleted Scenes 3 - YouTube (Alternative scene of Grace asking to become Augmented)