Prometheus just can't take a hint. The whole play, his friends—or what passes for friends—have been begging him to just apologize already, but instead he hurls insults and threats at Zeus. You can kill me all you want, he says, but I'm still not (1) going to apologize, or (2) tell you who's going to come along and kill you.
Bad move, dude. At the end of the play, Zeus takes Prometheus up on his offer. The stage rumbles with thunder and lightning, Zeus rains down some fury, and—finally—a gaping hole opens up in the face of the earth, and swallows Prometheus alive. Talk about a climax.
Like a lot of good climaxes, it leaves the ending open for a sequel. We already know that Zeus's big plan is to bury Prometheus for some indeterminate (but long) amount of time, and then let him out—so a vulture can come feast on his liver each day. (Tasty!) But we still have questions: (1) will Prometheus ever emerge from the pit?; (2) will he ever get free of his torment?; (3) will Zeus be kicked off his throne?
Too bad we'll never know. Prometheus Bound's sequel, Prometheus Unbound, didn't survive. That said, we think the sequel's title gives a good hint about what happens next.