Born in San Diego, California in October 1995. Ariel is the only child of Ellis and Diego Vargas. Her parents divorced when she was six years old and her father died in a car accident not long after.
When Ariel was eleven, her mother began to dating Gordon Fontana, who Ariel never truly liked. They got married two years later and Ellis become pregnant with Gordon's child (Ariel's half sister, Angela) the year after. Shortly after Ariel's 15th birthday, things took a dark turn for Ariel when Gordon turned violent and raped her in her bed one night and threatened to kill her mother and sister if she ever told anybody afterwards.
Ariel attempted to act as if nothing happened, but Gordon continued to secretly abuse her for years. When she was 18, Ariel moved out of her family's house for college. Years later, she moved to Los Angeles where she joined the police academy and was put on uniformed patrol duty after graduation. Despite moving out and become a police officer, Gordon still routinely visited abused Ariel and forced her to sleep with him, under the threat of committing the same abuse one Angela as well. Her relationship with her mother turned sour when Ariel cut off contact with Ellis to protect her and Angela's safety.
In the eighth season, a newly promoted Ariel went undercover and got involved in a case where two police officers were accused of raping a female colleague. Ariel caused trouble at first when she insulted Detective Beth Greico and Mike Ramsey after seeing them together at crime scene. Ariel and Beth got into a squabble, which resulted in Beth forcing Ariel to leave under threat of arrest, not knowing at the time that Ariel was an undercover detective.
The squad detested her meddling until Sergeant Chloe Hartman discovered that Ariel was D.A. Fontana's daughter and also a witness to the rape. Along with her video, which she filmed the officers, before and after the rape, Ariel testified against them along with several other civilian victims who came forward, resulting in the rapist officers' convictions and imprisonment. Captain Thorne decided to keep Vargas on until the detective she filled in for, Linda Young, returned from her leave of absence.
In Ariel's first official case with the MCU, the squad investigated the brutal stabbing of a woman in her own home. While the squad and the D.A.'s office suspected the victim's abusive ex-husband as the killer, Vargas listened to a couple of 9-1-1 calls the victim had made and realized that the ex-boyfriend of the victim's close friend is the true killer.
Ariel and Hartman tracked the victim's friend, finding her just as her ex turned up and was about to kill her. Ariel burst in and stopped him and she and Hartman arrest the killer. Ariel finished her shift and returned to her apartment where she found Gordon waiting for her. Ariel wasn't happy to see him; Gordon said he just wanted to talk, but then made a sexual advance towards and began touching and kissing her. Ariel, out of fear, ended up ultimately giving into Gordon's unwanted advances again.
At the start of the ninth season, Gordon had been on a business trip for three months, giving Ariel some degree of normalcy. But while babysitting Jack and Lauren's son Jason, Gordon returns, breaks into her apartment and holding Jason in his arms. When Ariel discovered them, she confronted Gordon and threatened to go public with his ongoing abuse against her, but Gordon not-so-subtly threatened harm against the Hartmans and her mother and sister if she did, even threatens to abuse Jason as a warning. After he gave her Jason and then left, Ariel, having had enough, declared war against her stepfather.
Ariel hired a group of teenagers to vandalize Gordon's car as her "first strike". The next day, she was forced to investigate the vandalizing of Gordon's car with other detectives. Ariel was satisfied when no evidence linking her to the crime turned up and was delighted about the teenagers over-vandalizing the car but later, Gordon secretly confronts Ariel at police locker room over the vandalism. Ariel strongly denied having anything to do with the crime, but a serious Gordon warned her that she will be sorry if he found out otherwise and then unzipped his pants, as a warning that he might sexually assault her again as punishment. Gordon leave, as Ariel promised he would be more sorry then she will.
A couple of weeks later, she ended up spending time with Gordon after he invited her to lunch at his house. Ariel tried to leave but Gordon wanted to take things further. Remembering Gordon's threat from several weeks before, Ariel tried to reject him but then saw Gordon's office keys and seeing an opportunity to gather evidence, she allowed him to have his way with her again. Later, Ariel stole Gordon's office keys and then tried to leave Gordon's house without anybody seeing her, but Deputy District Attorney Morgan Shane spotted her and confronted Ariel over Gordon.
Ariel told Morgan everything, including about her ongoing abuse, but is absolutely shocked when Shane reveals that she herself was repeatedly raped and abused by Gordon when she was teenager. Ariel told Morgan that she wants Gordon to pay for everything that he's done and Morgan informs her that she wants in. Morgan and Ariel plot against Gordon for months, but Gordon attempts to control both of them by framing Morgan for stealing drugs, for which she is arrested, but later released.
Hartman got involved in Vargas and Shane's recent secret activities after getting suspicious and confronting Ariel and Morgan. The two come clean about Gordon and the abuse they suffered because of him. Then Ariel tells Chloe about what happened with Jason, explaining that Gordon was threatens to abuse him. Horrified and disgusted, Hartman decided to help bring Gordon to justice, but was sworn to secrecy over the abuse until further notice.
Season 10 to 11
Vargas & Shane
Ariel is a hard-working and tough cop who wants to get justice for as many victims that she encounters as possible. She first struggles to comprehend justice in her own mind because her stepfather's longtime abuse. But when she gets involved with Chloe Hartman and the MCS, she finally begins understand everything and gains the drive to get justice for herself. After she does, she develops an huge sympathy spot for sexual abuse victims and a huge hatred for predators, especially those who abuse children.
- Jamie Delgado (boyfriend)
- Diego Vargas (father, deceased)
- Ellis Henderson (mother)
- Gordon Fontana (step-father, deceased)
- Miranda Aldridge (half-sister)
- Angela Fontana (half-sister)
- Graham Henderson (uncle)
- Lance Martinez (uncle)
- Diane Henderson (aunt)
- Alison Henderson (aunt)
- Rebecca Lanning (aunt)
- Sandra Martinez (aunt)
- Laura and Holly Aldridge (twin nieces, by Miranda)
- Charlie Aldridge (nephew, by Miranda)
- Mac Lanning (cousin, by Rebecca)
- Samantha Martinez (cousin)
- Unnamed cousins
- Eliza Martinez (great-cousin)
- Cara Vargas (grandmother)
- Service weapon: Glock 17
- An episode of Hartman season 9 mentions her birthdate as October 23, 1995.