Kai's mysterious past comes to light, when he was 4-and-a-half year old child was threatened. and his grandparents were sent to space by a trump slibings. When darlyn and friends notice he is not responding, still haunted by that treacherous event, they take him to the same nurse that sent his grandparents into space, unaware that the bear king and his crew is now going to send the first sins fighters to the moon, which will be darlyn and friends. Kai must save them after realizing that Wu,garmadon,darlyn and lloyd has become a major character in his life, besides his grandparents.
One day Kai notices a missing christmas character like children ad on the back of a milk carton and we are thrown into a series of flashbacks on how Kai was abandoned as a toddler. He had two grandparents that loved him very much, and one day, he got his head stuck in two gateposts. His grandparents took him to the nurse was laura jones where the pretty, estranged laura frees Kai and then asks to talk with his grandparents privately, warning of trump siblings. Little kai just overcome fear of spider to play and eat candy as little kai manages to save laura from sending into jail and watch his grandparents get nabbed by a net and taken away.
Kai and Laura follows the evil strange gangs and discovers the the strange gang is a trump siblings working on an experiment involving sending people up into space and breeding them in space and imprisoned children. Little Kai attempted to save his grand parents, but laura is arrest by cop and he is chased down a garbage chute by the trump siblings and he watches as his grandparents are blasted into space. And that was when Wu and garmadon found him and took him return his family and home.
As Kai remembers all of this, he goes into such a daze even darlyn's pet hamster as mouse doesn't snap him out of it. Worried, and Darlyn and a reluctant Her friends take him to the same doctor (former nurse an her evil nemesis, trump sibling) that blasted Kai's grandparents into space years before! Andre attempts to commit the stop same evil deed once again, but Courage escapes with laura and Andre and are pursued through the hospital by the evil villainn. They are eventually captured and taken to the trump sibling's hidden passages and laboratory. Darlyn and friends arrive just in time to get thrown into the rocket as well.
Kai,laura and Andre escapes and kai is chased around the lab. Kai knocks over a bucket of bolts and screws and dry ice, causing the pin poker,boo jack and skunk one to slip and freeze honey queen. He tries to open the door to the rocket, but to no avail. As the bear king shot him but kai was saved by laura, who is shot on her heart by bullet, as bear king nabs him again, Kai screams like tom cat as loud as he can into Andre's megaphone (which get from laura's supernatural box of tools that Andre took for himself after dropped into floor by kai). Andre then grabs the key, unlocks the door and saves kai's friends and then manages to trap the evil crews inside the rocket and then the evil vet is blasted into space. The final episode ends with the evil trump sibling landing on the moon surrounded by all the angry mob of adult and old people that they blasted into space, including group of children, Kai's grandparents and laura's ghost. They are then seriously beaten (most likely killed) unmercifully by the angry mob off screen.