Agents Olympia and Otis meet the Xs, who were sent to make sure the Odd Squad Headquarters is not breaking any rules. The Xs find that the Headquarters is over budget by $100. They explain to Olympia and Otis what a budget is, and the two agents have until the end of the day to lower Headquarters' spending or it will be shut down permanently.
Ms. O tells a story about the hydraclops' attack on the Odd Squad headquarters. One of the agents finds out what each hydraclops dislikes and represents their dislikes in a venn diagram. Unfortunately, the team has only enough time to fire one shot at both hydraclops, so they will need to find something that both of them dislike. Ms. O explains venn diagrams to the team and uses one to find a mutual dislike: eggs yolks.
Olympia and Otis attempt to intercept a dancing villain, who makes her victims dance forever. The villain strikes at different parts of town, and the duo guessed her attack pattern incorrectly. They determine that she will strike the mayor's home next after discovering the real pattern.
Zeros are disappearing across town, and Olive and Otto visit Polly for some hot chocolate and help. Polly shows bar graphs of her profit for each day of the week to the two agents, and she notes that her profit for the current day is much lower than usual. Olive points out that Polly's lower price is contributing to her lower profit and explains to Otto why zeros disappearing is a problem. In her explanation, Olive illustrates the difference between 1, 10, 100, and 1,000 marshmallows.
On Christmas Eve, Ms. O is surprised to learn from Santa that she is on his naughty list. Santa shows her that she has performed more naughty actions than nice actions and explains his use of the "greater than" symbol. Unless she performs more nice actions than naughty actions before Christmas, Ms. O will not receive any presents.