The mane 6, Spike and The Cutie Mark Crusaders go deep down into the Everfree and find a secret forcefield and they step into it and they turn into cats and join ThunderClan and start understanding the ways of The Warrior Code and decide to stay there until they find the forcefield again. Will they find the forcefield or will they have to stay cats and say goodbye to Equestria forever?
The picture is what they look like in the story if you didn't know what they looked like. Also, the story takes place in the forest before they moved to the lake and it takes place before Firestar's death...SPOILER ALRET!!!!!!!!!!!!!!!
It takes place after the cutie mark crusaders get their cutie marks in season 5.