Using imagination, reasoning, and boundless enthusiasm, inventor Addison loves to solve mysteries with her friends.
When Addison and Alex taste the new pizza that Mr. DiGiovanni has created especially for Tess’s birthday, they find out it doesn’t taste good at all and so they set out to investigate what the problem is. Has Mr. DiGiovanni lost his sense of taste?
Ms. Bell's wedding is in peril when a ghost scares away the customers from the beauty salon where everyone is getting ready for the ceremony. But Addison thinks the rumbling and drafts might have natural causes.
Addison goes undercover when it appears that someone is stealing raspberries from the community garden – raspberries that she and Tess need to get their next Ayrton Rangers badges.
Addison has to figure out why Alex can't kick a soccer ball nearly as well as he used to, in order to correct his game in time for him to pass the team tryouts. Alex thinks he's jinxed, but Donnie has a vested interest in making sure Alex doesn't make the team.
Addison, Kevin and Tess are trying to make a rap music video for Ayrton Park’s Summer Fest Movie Night, but a persistent very LOUD buzzing from above keeps ruining everything! Addison sets out to solve the mystery of what’s making all the noise.
When Tess and Alex suddenly start getting electric shocks for no apparent reason, Addison has to solve the mystery or it will be lights out on their act for the school talent competition.
During a summer heat wave, something or someone – perhaps a cryptid Camenel – keeps draining the water from the wading pool.
When Ms. Bell’s prized apple-hologram marble – a gift from her own favourite teacher at teachers’ college – goes missing, Addison is on the case to find out how it disappeared from inside the locked classroom.
When Donnie, the obnoxious class semi-bully seems to have developed psychic powers, Addison has to figure out how he's doing it and stop him from intimidating the other kids.
When Gyro the robot appears to be unhappy, Addison has to figure out what's wrong with her little friend.
When the honey in the community garden's beehive turns bright indigo, Addison is on the case to find out what's giving the bees the blues.
When it appears that half of the cookies Tess and Addison baked for a charity event go missing, the girls are mystified. Could somebody have eaten an entire table of cookies? With a trail of crumbs as a clue, they chase the cookie crunching culprit.
The annual winter carnival seems to be in trouble when Addison and Alex's yeti sculpture appears to have been vandalized… perhaps by an actual angry yeti!
