Turn off Autoplay on the Timeline tab, and keep Up Next empty.
When an episode ends, Castria plays the next one in Up Next. When Up Next is empty, it carries on with the next episode in your Timeline. Those are two separate things.
- To stop it continuing into your Timeline: open the Timeline tab and turn off Autoplay. The switch is just below the top episode. It's on by default, and you set it separately on each device.
- To stop it playing your queue: clear Up Next (see How do I reorder or clear Up Next?). Episodes in Up Next always play in order.
To stop after a single episode, set the sleep timer to End of episode. See How do I set a sleep timer?