Horizon/Season One

 Episodes Border Rattle and Pebble are caught in a harsh storm. Rattle wakes up and realizes that he and Pebble are dead. But to his horror, Pebble is in Acheron, the land of the damned. Rattle knows that at the very least, he should be there and she should be in the heaven of Avalon. But there's a barrier, a border between the cats of Avalon and the cats of Acheron that seems uncrossable.