In "
Lockdown", Thirteen says she went to
Newton North High School. In "
Epic Fail", Thirteen reveals she attended
Sarah Lawrence College. The episode "
Let Them Eat Cake" shows that as a child she resented her mother, who was dying from Huntington's, and she tells
Chase that she knew her father was having an affair; other than this, very little is shown about her past. She appears to be very street-smart; she can easily identify a drug dealer and is also able to differentiate between high-purity and low-purity
cocaine by the strength of the numbing effect on her gums, as well as identify typical street-level drug-dealer tactics employed to ensure repeat customers. At the end of the fellowship competition,
Lisa Cuddy tells House that, since he already has Eric Foreman on his team, he may only hire two additional people, so House fires Thirteen and Amber, claiming fellow applicants
Chris Taub and
Lawrence Kutner outperformed her, and that if he could keep Thirteen, he would. Cuddy overrules House's decision, forcing him to accept a woman, realizing only a minute later that this had been House's plan from the start. Several episodes later, Foreman and Thirteen embark on a relationship, which affects Foreman's professional judgment to the extent that he fixes the drug trial, which causes serious side effects in Thirteen. Foreman almost loses his medical license, resulting in House ordering the couple to either break up or quit. The couple fake a split and continue their relationship in secret, but come public after House discovers they are still seeing each other. Initial relationship strains develop during the episode "Simple Explanation (5.20)" when Foreman tells Thirteen he needs time to himself to grieve and process Kutner's suicide. The conflict is resolved during the funeral when Foreman reaches out for Thirteen's hand, and Thirteen, surprised by the gesture, accepts. When Foreman takes House's position in the sixth season, Thirteen's relationship with Foreman becomes strained due to their difficulties balancing their romantic relationship and their new employer-employee status at work. Foreman fires Thirteen in "
Epic Fail" in an attempt to save their relationship, which fails. Thirteen initially breaks up with Foreman but later decides to try to work things out by agreeing to dinner with him; when, at dinner, she asks if he would have ever considered stepping down from the head of the diagnostics department rather than sacrifice either her career or their relationship and Foreman replies no, she leaves him for good. In the sixth-season episode "
Instant Karma", Thirteen attempts to book a one-way flight to
Bangkok, Thailand, citing a need for a vacation. However, the tickets are mysteriously canceled, and Thirteen confronts House, Cuddy and Wilson to find out who did it. Wilson confesses to hacking Thirteen's e-mail account, but it is later shown that it was really House. House is evasive about whether he did it for his own benefit, Foreman's or Thirteen's, but Wilson surmises that it is simply because he likes having her around and he needs her. Thirteen is seen eventually boarding a plane. In the episode "Teamwork", Thirteen has returned from Thailand and House manages to convince her to return to his team along with Chase, Taub, and Foreman. During the season-six finale, "
Help Me", Thirteen shows up late at a differential, obviously hiding something. She leaves a letter on House's desk asking for leave, citing personal reasons; when Taub asks her if everything is okay, she replies "obviously not". In the season-seven premiere "
Now What", Foreman reads her letter and goes through her locker, finding flight tickets as well as information on an experimental treatment for Huntington's in
Rome. With her teammates believing she will be leaving for Rome the following day, Thirteen affirms her friendship with Foreman and Taub tells her he approves of her seeking any chance of getting better. Chase offers her a sexual proposition (in the same way he once did
Cameron), but she turns him down and surprises him with a long embrace. The team organize to meet up and have cake to send her off, but Thirteen disappears without saying goodbye. Foreman then discovers that the clues about Rome were purposely planted by Thirteen as a
red herring. The team later find that all her phone lines have been disconnected and her apartment has been vacated. Following this, Thirteen remains missing for a year without anyone knowing of her whereabouts. Her vacancy in the team is eventually filled by
Martha Masters. Thirteen returns in the show's 150th episode, "
The Dig", where House meets her upon release from a prison where she has been incarcerated for the last six months for over-prescribing drugs. She has House drive her to a seemingly random house where she rings the bell, then assaults the man who answers the door. The two then spend a few days on the road preparing for a
spud-shooting contest while House tries to figure out the real reason Thirteen was in prison, eventually deducing that Thirteen
helped kill her brother, who was suffering from advanced stages of Huntington's. Thirteen eventually admits to House that she did what she had to when her brother's time had come, and that now she is alone and will have nobody there for her when her time comes. House later tells her that he is willing to euthanise her when she needs him to and rehires her onto his team. The rest of the team are excited to see Thirteen again and are curious about where she has been; to her chagrin, House tells the team that she has been in
rehab for a substance abuse problem. She
later tells Masters, "the real reason I was gone is not something I want to share." Upon her return to work, House notices a change in her personality, as she has become more cynical and
fatalistic, appearing resigned to misery. House eventually concludes that if Thirteen can convince herself that she is naturally miserable as a person, then she does not have to hate the universe for making her miserable. Thirteen then turns around, pointing out that House's life is also miserable, and that "We are who we are. Lotteries are stupid." In "After Hours", a then-unknown woman arrives at Thirteen's apartment with a serious wound in her abdomen. She is revealed to be a cellmate of Thirteen's from prison and makes Thirteen promise that Thirteen will not take her to a hospital, as she will be arrested and taken back to prison. Thirteen phones
Chase requesting help on false pretenses, bartering on their relationship to convince him to bring medical supplies without explanation. Chase convinces her to let him help, and she admits to him that she was in prison for killing her brother. After it becomes clear the woman will die without a hospital, Chase engages in a physical confrontation with Thirteen to get the patient to the hospital. He also deduces that her conviction to always keep promises is so that she can blame her brother's death on her promise to him, rather than blame herself. After the two drive the woman to the hospital, she awakes alive but in custody. Thirteen apologizes, but her friend lashes out, claiming she only used Thirteen because she needed someone to talk to in prison. Thirteen later confides in Chase that his theory is right, and that she is afraid she will be consumed by guilt. In "
Charity Case", Thirteen is called in once more by House to help solve a case. She then decides to join the team once more. In the end, House sees that Thirteen was happy with her girlfriend and fires her once and for all so she can live out her last days being happy. She makes her final appearance as one of the speakers at House's funeral (House faked his death, only ever telling Wilson, who is in the final months of his own terminal illness) in the series finale "
Everybody Dies". == Concept and creation ==