Grace "Gracie" Williams is the daughter of Detective Sergeant Danny Williams (2010) and Rachel Edwards, Danny's ex-wife and stepdaughter to Stan Edwards and the sister of Charles Edwards, Stan and Rachel's son.
Grace being brought to Hawaii is the sole reason Danny quit his job and came to Hawaii, first joining the Honolulu Police Department and eventually the Hawaii Five-0 Task Force.
Whenever Grace is not with Rachel and Stan, she usually stays with Danny on weeks. Every Christmas, Danny dresses up as Santa Clause to surprise.
Due to her father teaching her, Grace is also skilled at poker.
Danny has one of her drawings and a toy police car in his office, as well as a picture of her when she was younger. She also drew him a picture when he was hospitalized for Sarin poisoning. Sometimes at night Grace uses her phone to call her father.
As her father, Danny takes Grace's safety and well-being very seriously, often reacting in a violent and frightening manner if he feels like that Grace's life has been jeopardized which is seen during E Malama (episode) and Mai Ka Wa Kahiko (episode).
Grace appears to have lots of friends at her school. Danny tries to balance out her privileged upbringing with her mother and stepfather. Grace refers to her father's partner, Lieutenant Commander Steve McGarrett (2010) as her "Uncle Steve".
Grace is somewhat shy/wary around new people, with the exception of her father's teammates, whom it is implied he speaks of often.
Grace likes pink, Hello Kitty (dolls, laptop), sports (baseball, tennis, football) and animals. She has two pets, a rabbit (Mr. Hoppy) and an unnamed male dog previously belonging to Agent Monica Jennsen.
- Monkey- (Danny calls her this).
- Gracie- (Steve calls her this).
Grace is first seen in the Pilot when Danny drives her to school.
In 1.03, 'Malama Ka Aina' ('Respect the Land'), Grace attends a Kukui High School football game with Danno where she meets Steve, Kono, and Chin for the first time. However, a gang related shooting cuts her visit short and causes Rachel to feel concern over her safety around Danny.
In 2.15, 'Mai Ka Wa Kahiko' ('Out of the Past'), Grace is kidnapped by Danny's ex-partner who spent ten years in jail due to Danny's testimony. This forces Danny to go off the grid to save Grace's life and he even shows his darker side which is demonstrated when he shoots Peterson in the kneecap to force to him to give up Grace's location. Despite this, Peterson refuses and Danny threatens to shoot Peterson in the head, forcing Peterson to give in.
In the finale, her mother and stepfather are planning to move to Las Vegas for Stan's job. Danny eventually calls Rachel and tells her that he'll see her in court.
In 3.06, 'I Ka Wa Mamua' ('In a Time Past'), it is implied that Grace was named for Det. Grace Tillwell, her father's partner, who died before she was born.
In 3.10, 'Huaka'i Kula' ('Field Trip), an Aloha Girls camping trip with Grace turns deadly when an armed man takes Steve and a girl hostage.
Danny recently won the right to keep Grace with him in Hawaii, instead of moving to Nevada to live with her stepfather.