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 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 Whitefetaher & 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 moving 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 Daryl 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.