Sydney is turning 13 and sets out to plan a sophisticated birthday party. Her plans remind Max of when he tried to organize his own surprise party for his thirteenth birthday back in the 90s.
Sydney and her friends make a pact to go to the dance together without dates. Max recalls his first school dance when Leo and his Mom gave him tips on how to ask a girl to be his date.
When Sydney and Olive accidentally destroy a very popular exhibit at the museum, their teacher Mrs. Harris is deemed at fault and in jeopardy of losing her job. The girls devise a plan to convince VP Virmani not to fire Mrs. Harris.
Something embarrassing happens to Sydney while at school, so she holes up in her bedroom. She finds old VHS tapes of Max as a kid, falls asleep and dreams she's in the 90's.
In an effort to save the planet, Sydney and her friends stage a student protest to convince the cafeteria to go green. Back in the '90s, Max and Leo fight to keep their school from getting rid of the junk food in the vending machine.
The memory of her late mother and some long-forgotten advice helps Sydney rediscover her love of Christmas again, a holiday she has avoided ever since her mother passed away.
Sydney is excited when she makes the school's first girls fencing team. But when she learns her dad helped Coach Carlock, Sydney fears she may have gotten on the team for the wrong reason.