Your main cat has the ability to turn into another cat, they must keep this ability hidden at all costs. The cats should both be from different clans and look differently to each other. one day, while your cat is at a gathering, a cat from the other clan your main cat is in grows suspicious of why their clanmate never comes to gatherings at the same time as your cats other form. They ask your cat questions about this to see if they could get proof that you and their clanmate not showing up are connected, when your cat slips up and reveals something connecting the two the cat grows more and more suspicious. The cat does this at every gathering your main cat goes to, the main cat slips up more and more with their frequent questions, the other cat does this to both of the cats forms and eventually figures it out, they confront your main cat about it. your cat could deny it or give in and tell the truth, either one would do more for the plot. If you want to add more to the story, you could make it so that one of or both of your cats forms develops a mind. Their forms developing a mind starts to confuse your cat, your cats Mind gets over powered making their forms into new cats with their cats own personality, if you choose to do this you could keep the focus of the story on your original cat, or change it to thw forms developing their own personality.
Sorry if the end got confusing; but it's basically that the two cats they can turn into gain their own personality's and the main character could be sent up to StarClan, or wander as a spirit.
