The upcoming trial over a death on the set of the “Walking Dead” zombie drama will hinge on one key question: What happened in the moments before a stuntman plunged off a balcony and missed an airbag 20 feet below.

Lawyers for the AMC television series and its producers have argued that they are not to blame and that John Bernecker assumed the risk of his dangerous job. But lawyers for his parents, Susan and Hagen Bernecker, say something went wrong on that balcony.