Mia is still getting used to having her new stepdad and stepbrother around when she begins to struggle with writing in her Spanish class, and since her family, who speaks Spanish, is willing to help, Mia learns that she is lucky to have three parents.
Aspiring to win the science fair with a project that proves that cupcakes are good for you, Alexis finds her ambitions challenged by her crush's association with another girl and a cupcake order for a mean girl's sweet sixteen.
Worrying about her fashion prospects when she learns that she has to get both braces and glasses, Mia receives help from her stylish mom and is reassured by her Cupcake Club friends that she is still the same old Mia.
In the midst of a terrible week, Mia receives a lucky charm from her cousins from Puerto Rico, and when her luck turns around, she attributes it to the charm, but when her bad luck returns, she must come to grips with the truth.
When Emma's little brother Jake looks after the neighbor's dog in preparation for getting his own puppy, the pet goes missing and Emma and the rest of the girls have to find it before the owner comes home.
When Sierra's parents decide to foster a cat and her three kittens, Sierra must juggle her other responsibilities, including school, captaining the softball team, and working at the ice cream shop, with caring for the cats.
Reaching a compromise with her parents when they say she is too young to attend a concert alone, Mia discovers that she is being cyberbullied on social media and teams up with her fellow Cupcake Club members to discover who is behind the attacks.
When Sydney moves away and is replaced by newcomer Olivia, Alexis becomes the focus of hurtful teasing by the Best Friends Club and begins to wonder if an offhand remark she made when first meeting Olivia may have been taken the wrong way.
After her aunt dies, Kelsey's cousin Lindsay, who also works at the donut counter at the family restaurant, is invited to more family only activities and Kelsey starts to resent the extra time her cousin spends with her immediate family.
"Sierra is tired of being known as the sweetest girl in the ice cream shop, but she still wants everybody to like her! Can she spice up her personality (and learn to say no occasionally), and still keep all her friends? Sierra decides to pour her feelings into an original song, and through music, she's able to find her voice"--Provided by publisher.