Any creative ideas to prevent people from stealing a DVD from an opened DVD set?

I have a bunch of DVD sets I need to resell. Mostly TV series seasons. 3–10 DVDs to a set. My biggest fear is someone stealing one disc out of the set, ruining the value.

Taking all the discs out and storing them separately isn’t really an option. I don’t own the store where they will be selling, and that’s too much of a hassle. I have a locked glass case at each place, but there are too many DVDs for that.

Any creative ideas?