The Teammates crew plan for the Dog Pageant and get tied up with a murder mystery. But, when Jones friend with his old friend Darlyn and Lloyd left to solve the case.
The victim Molly Robinson is bludgeoned to death with her own lamp by an unseen assailant he recognizes while caring her dog; she is the latest of twelve victim to be killed. Meanwhile, Darlyn, lloyd and jones are running a "Training mentor and mentee" academy service from their chief On one such training, the police save Margaret littlewood, a former pin-up girl mascot for the Dog Pageant company, and her miniature dog, Astrid, when the brakes on her bike appear to fail. They drive alongside so Jones can attempt to use pastries to stop, but they careen into a zoo and barely escape being eaten by a crocodile. Darlyn tests the bicycle brakes and becomes suspicious on learning that the brakes work perfectly fine, but Jones becomes friend with Margaret.
A whirlwind friendship ensues, during which it is also shown that the nervous Astrid is treated rather shabbily by Margaret. During the hang out B.F.F, Margaret gives the entire house a "Best friend forever," decorating the whole house with dog friendship pictures and flowers (including Darlyn's training room). In addition, she pushes Darlyn out of her relationship with Jones and spends more and more time with him. Angry that Margaret has interrupted her relationship with Jones and modified the house, Darlyn is about to start destroying the decorations when Astrid stops by her room. Astrid and Darlyn share a sensitive moment after she timidly returns Darlyn's possessions, which have been discarded by Margaret. However, when Margaret leaves her purse at the house, Jones decides to return it, but it is raining outside. Not wanting to get wet, he insists that Darlyn and Lloyd return it instead. Upon arriving at Margaret's affluent mansion, Darlyn discovers several dressmaker's dummies in her bedroom, each wearing a People's Clothes. In a book, Darlyn discovers photographs of Margaret with the murdered victim. To her horror, Lloyd discovers Margaret is the "serial Killer" as he discovers a picture with Their mentor, Jones as her apparent intended thirteenth victim, thus completing a "victim's dozen." Darlyn accidentally knocks over all the dummies, but gets them all back up again before Mrs. littlewood enters the bedroom, escaping detection by hanging from the chandelier with lloyd. Despite Margaret's lavish ways, Astrid has to sleep in an cardboard box, covered with a tattered rag, implying years of mistreatment.
Despite Jones being oblivious, Darlyn and Lloyd attempts to thwart Margaret by installing an airport-style metal detector in their home. After tricking Jones into thinking that Darlyn attack her, Margaret almost succeeds at pushing Jones to his death whilst a chained up Darlyn and Lloyd can only watch, but she is thwarted by being struck by a bag of gravel from their mixing contraption. After an angry outburst against Their mentor, she leaves but returns a day later to apologise with a large cake. Jones says that it will do nicely for four o'clock coffee. When Margaret is leaving to attend to the absent Astrid (who is "not well"), she tells him he will be getting a surprise. A worried Darlyn and Lloyd follows her home only to be caught and imprisoned with Astrid, Dianne and Window in a storeroom. Escaping in Margaret's old hot air balloon, they arrive at Dog Pageant as he is lighting the candle with their Little Helpers.
After a struggle, the cake falls to the floor and a bomb inside is revealed. While attempting to dispose of the bomb, Jones, Darlyn and Lloyd are attacked by Margaret, who reveals she is the "serial killer" and detests owners of dogs and their creations for ruining her figure and her wining trophy and Medal/Badge as the Dog Pageant winner after her obesity from consuming too many pastries meant she could not ride her balloon anymore. While attempting to finish off Jones, a battle ensues between Margaret and Astrid in a yellow forklift truck covered by giant gloves.
In the chaos, the bomb ends up in the back of Kai's towel after The Little helpers accidentally put the bomb on it during attack. Jones, Darlyn, Lloyd and Astrid neutralize the explosion using a large amount of ice creams while Margaret uses the distraction to leap onto her balloon and escape. However, owing to her fuels, the balloon crashes into the crocodile pit at the zoo where she is eaten alive (off-screen). The balloon floats away with Littlewood's ghost (her former slim young self) waving goodbye to The Teammates Crew. Distraught by the death of her owner, Astrid leaves, with Darlyn, Lloyd and Jones depressed over their losses (though Darlyn cheers up after a good time for winning while Jones is still upset about his pet). Deciding to take their minds off things, they head out to take the killer down and find Astrid (Found by Naomy who give jones a pet.) standing in the driveway, uncertain as to what to do or where to go. They joins them in the van and the others drive off into the sunset.