Addison has to solve the mystery of what's making scary sounds after Donnie convinces the other kids on an Ayrton Rangers camping trip that a mythical spook called the Headless Haunter is wandering through the park.
When swarms of mosquitoes mysteriously descend on the park, the kids' summer movie night is in danger of being canceled unless Addison and her friends can figure out a way to stop them.
When Addison and her classmates get a school assignment to write about local news - and the news is that laundry is going missing from balconies around Ayrton Park - Addison turns investigative reporter to crack the case and get a scoop.
When Addison and her classmates get a school assignment to write about local news - and the news is that laundry is going missing from balconies around Ayrton Park - Addison turns investigative reporter to crack the case and get a scoop.
Addison's excitement at bringing Eureka and Gyro in for a show and tell at school turns when Donnie has a robot that can do everything hers can, but better. There has to be a sneaky mystery involved, and Addison is determined to solve it.
Addison and Alex's soap box derby car seems like a shoo-in to win the annual race - until something or someone makes it mysteriously slow down to a crawl. Has it been sabotaged? Addison only has an hour till race time to solve the mystery.
When Kevin's new radio-controlled model car starts acting like it has a bad-tempered mind of its own, he becomes convinced that it is haunted and asks Addison to help.
When helium balloons for Tess's fashion show start inexplicably popping, she is upset and asks Addison to help her figure out the cause and stop the rest of the balloons from popping before her show is RUINED!.
Addison and her friends are distracted from their mission of making cool costumes for Ayrton Park's version of Comicon when someone or something starts messing with recycling bins all over the neighbourhood.
Addison's plans for a local version of the winter Olympics are in jeopardy unless she can figure out why their outdoor ice skating rink keeps mysteriously melting and running away.
Addison fears that her family and friends have forgotten her birthday, so instead, she takes consolation in trying to solve a series of mysterious clues that take her on a wild goose chase all over Ayrton Park.
Addison and Tess make a haunted maze for Halloween, but things take a perplexing turn when it seems that there really is a spooky presence on the loose within it - scaring away all their customers.
When Mrs. Rorschach suddenly develops an allergy, every indicator points to Mr. Tiggles as the cause. Addison has to solve the mystery before Mrs. Rorschach and her kitty are forced to part ways forever.
Ms. Bell plans to surprise her students by hiding mammoth fossils in the school sandpit so they can dig them up. But the surprise is on Ms. Bell and her students when the fossils disappear - and Addison has to figure out where they went.
When crop circles begin appearing in Ayrton Park, Alex suspects visitors from the fourth dimension, but Addison begins sleuthing in search of a different explanation.
When Addison and Tess find a note in a funny old pair of rummage sale pants, they think they may have found a clue to lead them to a stash of priceless hidden diamonds.
When the school mean girls, Katie and Dinara, start their own detective agency and solve a rash of neighbourhood mysteries before Addison can, she wonders if she's lost her touch...or if there is something else more nefarious going on.
Addison and her classmates are tasked with playing a piece of music written by the local billionaire, who has promised to donate to the school's music program - but if Addison can solve a musical puzzle and fill in the blanks in the music.
Addison's and Tess's fairy garden school project attracts a mysterious glowing frog. While Alex thinks it's radioactive and Tess believes it's a magical fairy frog, Addison is determined to find the real answer to this amphibious mystery.
When the fish in the local pond all seem to disappear, Addison and Tess fear that they ended up as fish sticks in the school cafeteria's lunch special and set out to solve the mystery.
Addison and Alex are afraid that Mrs. Rorschach is being secretly intimidated by a shadowy pro wrestler named the Lucha Grandma and are determined to find out her identity and put a stop to her antics.
When it appears that a midnight vandal is damaging Max's entry in the town's "Most Beautiful Public Garden" project, Addison goes undercover ninja to save the day.
When a highly advanced computer is loaned to Ayrton Park Public School, mysterious cyber events begin happening around town and Addison wonders if the occurrences could be part of a world-wide-web - of mystery.
When a lost parrot appears in Ayrton Park, Addison must find some way of returning it to its rightful owner by deciphering clues from the cryptic phrases that the errant bird utters.
Addison and Alex are filming a class-project documentary about a "typical day in Ayrton Park" - but things quickly become anything but typical when a mysterious fog envelops the entire downtown area.
Addison has a double challenge: finding out who is behind a series of strange thefts, and then when she does discover who the perpetrator is (her mother, the detective), getting to the bottom of why her mom has gone to the dark side
