Nathaniel Plimpton III is a Stanford educated lawyer and majority co-owner of Whitefeather & Associates. He is from a prominent Los Angeles family who run the law firm of Plimpton, Plimpton & Plimpton. Nathaniel and his family were looking to extend their business into the San Gabriel Valley and bought the West Covina firm as part of that expansion. Nathaniel's brusque, elitist and no-nonsense personality made him unpopular with his employees but since moving to West Covina and interacting with his staff his attitude has softened somewhat. This is particularly in regards to Rebecca Bunch whom he confessed to have feelings for. His time with Rebecca led to him making changes in both his attitude and his personal and professional life. Ultimately Nathaniel quit his job at his father’s law firm and became a legal consul for a South American zoo. His is first appearance was in the Season Two episode "When Do I Get to Spend Time With Josh?". He is portrayed by actor Scott Michael Foster.
In order to expand his family's business further Nathaniel Plimpton III purchased a stake in a small West Covina law firm called Whitefeather & Associates. His elitist attitude and insistence that the staff work twice as hard rubbed his new employees the wrong way particularly the star attorney Rebecca Bunch. After a rocky start, including Rebecca assaulting him, an unexpected attraction developed between them. This led to them kissing after they were trapped in an elevator. He correctly guessed that because of this, Rebecca moved up her wedding date to Josh Chan. Despite his initial poor treatment of Darryl they also began to form a bond; Darryl looked after Nathaniel when he had a treadmill accident and when he got sick from a homemade health drink. Eventually Nathaniel started to show a softer side. Upon hearing Rebecca's father wasn't coming to her wedding he had his private jet fly Silas in for the ceremony. Nathaniel attended the ceremony and witnessed along with the other attendees that Josh abandoned Rebecca at the altar. When Rebecca had a breakdown and turned her fury at being jilted towards her father, Nathaniel refused to let Silas use his jet again to fly home.
In the fall of 2016, on Nathaniel Plimpton III's first day as the new co-owner of Whitefeather & Associates he called a staff meeting in the boardroom. He chastised the firm's star attorney Rebecca Bunch for arriving late and insisted she make her job her main priority. Nathaniel was unfazed when she quit since without her on payroll he could fire fewer employees. Rebecca took back her resignation and assured Nathaniel she could bring in revenue to avoid lay offs. He gave her until the end of the week and went to have lunch with Darryl at Home Base. When Darryl advised he tone down his management style Nathaniel informed him he was now the sole boss as he had bought additional shares of the firm from Darryl's ex-wife. Afterwards Nathaniel was told by Rebecca that she lined up a meeting with a potential client.
However, she was unable to secure a contract so Nathaniel proved he was serious about the deadline by firing George(♫ George's Turn ♫). Later, Nathaniel teased Rebecca at a restaurant where she was having dinner with her fiancée and his parents. The next day Nathaniel was about to fire several employees wheh he was interrupted by Rebecca and Paula. Having failed to get a client, Rebecca pleaded with Nathaniel in private to reconsider. When Nathaniel insulted both her and Josh, Rebecca assaulted him with a pen. As Nathan struggled with Rebecca the potential clients from the other day showed up. Despite witnessing the scene they hired the firm anyway and Nathaniel announced that everyone's job was safe for now ("When Do I Get to Spend Time With Josh?").
Sometime later, Nathaniel discovered a Treadmill desk in storage at the office and had it cleaned and installed in his office. As he excercised on the treadmill, he was interrupted by Darryl who made some inadvertent scatalogical references. Once Darryl left Rebecca showed up to tell him she was using her vacation days to take a trip back home to Scarsdale with Josh.
Nathaniel is worried about Rebecca after Josh left her at the altar and is both relieved and shocked when she returns to work with a new attitude. He is eager to help when she asks him to help her get back at Josh. They finally consummate their relationship but she rejects him after learning he went to far in his plans to get revenge on Josh. Nathaniel confesses his feelings for her but an intervention staged by her friends interrupts the moment. He learns about Rebecca’s past and is forced to replace her at the firm when she quits and decides to move back to New York. When Rebecca returns to West Covina after a suicide attempt Nathaniel is sympathetic after remembering a similar incident he experienced in his childhood. After her recovery, Nathaniel and Rebecca start dating but it ends shortly after a she has a misunderstanding with his father. Heartbroken, Nathaniel officially fires Rebecca and starts dating Mona. Rebeca retaliates by using a legal loophole to acquire controlling interest in the law firm. This rekindles the attraction between them and Nathaniel and Rebecca start having a secret affair. This ends after several months and Nathaniel refocuses on his relationship with Mona. He and Mona decide to move in together and had a big housewarming party. Rebecca’s supposed boyfriend Trent disguised himself as a waiter to get revenge on Rebecca breaking his heart. He intended to kill Nathaniel but Rebecca intervened and pushed him off the balcony of the high rise complex the party was being held. When Rebecca was arrested for gopher actions Nathaniel acted as her attorney and advised she cite temporary insanity as her defense. Much to Nathaniel’s disappointment she ended up pleading guilty.
Nathaniel got upset when Rebecca rejected his legal counsel for her trial and went on a dangerous wilderness adventure trip to distract himself. He returned home after learning Rebecca was acquitted of all charges but she told him that can’t be together. Nathaniel gives Rebecca the cold shoulder when she’s returns to work but has a realization that he still loves her. After a scheme to win her back backfires she bluntly tells him they are done for good. Nathaniel's professional life gets bad too when his father puts Bert Buttenweiser in charge of the firm. He receives sad news that his childhood nanny passed away and with Heather's help he fulfills a promise he made to her. Nathaniel discovered Paula using company time to help out at Rebecca's free legal clinic and in an effort to become a better person offers his own services. At the gym he meets and befriends Greg Serrano only to learn he was once an ex-boyfriend of Rebecca's. Nathaniel got invited to game night at the Proctor's and learned Rebecca and Greg got back together. After some agonizing he accepted she moved on and tried to do so himself. However, once he found out Greg and Rebecca broke up he decided to pursue her again. This culminated in all three former boyfriends competing in a contest to win her affections. Despite Nathaniel's best efforts she didn’t choose him or any other of the candidates. His last rejection caused him to make a life changing decision and he quit being an attorney for his father's firm. Nathaniel moved to South America and became a lawyer for a zoo. A year later he came back to West Covina to see Rebecca perform her music alongside all her other friends.