Q: One episode of a TV show download will not open, all others worked. What to do?

Delete it and redownload. It may be corrupted.

Try deleting the episode and downloading it again.

Swipe on the episode to one side to bring up the Delete button. Tap it to delete.

Then go to the iTunes Store, tap un Purchased, and look for your episode. when you find it tap on the small cloud button to download it.