Iris (Toni Collette) is a very mousy and quiet young professional who doesn't want to "rock the boat" at the office where she works as a temp employee. Margaret (Parker Posey) is the polar opposite to Iris and a catalyst to help her change and speak up for herself. Paula (Lisa Kudrow) eagerly awaits post-work Happy Hours at a local bar and the chance to hook up with the company's executives. Jane (Alanna Ubach) is engaged to marry a jerk who is already cheating on her. Margaret hopes to become a permanent employee as an assistant to Mr. Lasky (Bob Balaban) but her dreams are thwarted when he suddenly dies.A series of thefts start to occur in the office and suspicion falls on the four temps, particularly Margaret. When Iris finds a plastic monkey that she thought was stolen inside Margaret's desk, she loses faith in her and believes she has been doing the stealing. Margaret suggest a one-day strike from work and her friends halfheartedly agree to join her, but on the appointed day, Margaret is ultimately the only one who does not come to work. As a result, the company's officious HR head (Debra Jo Rupp) fires Margaret, and management begins to micromanage the remaining three employees.Iris and the other women's friendships come to an end, as result of the stress, and eventually they all go their separate ways. Jane soon quits her job. Paula reveals that she only heard about Jane's wedding via a newspaper article and Paula goes to temp in another department.It is later revealed that another employee, a shy, quiet young woman from a rich household who became a permanent employee on her first day, was the culprit and that Margaret simply had an identical toy in her desk. Iris confronts the young woman when her diary (from which she does the film's narration) goes missing, and later receives a new diary and note of apology. Iris later is not hired for a job she really wanted, but ironically this helps motivate her to quit the temp field and move on. But before she leaves the company, she is able to do Margaret a favor: one of the senior executives agrees to sign a letter of recommendation for Iris, but she tells him her name is Margaret and, since he had not bothered to learn any of the temps' names, he does not know the difference. Iris then mails the letter to Margaret and bids the temporary worker goodbye.