Here's how things happen when I write. My hero's side is trying to make progress on who's murdering his associates. The associates are beings who used to be Greek gods, so they have some advantages.
The nominal leader of his cause wants to send him on a mission, and he doesn't know the technique to get where he wants to go. (He needs to get to the Underworld). No problem. By surprise, she stabs him in the heart. Now he's at the Underworld.
It was a spur of the moment decision, and led to a half chapter of hero's journey as he dealt with the Underworld. Luckily, I needed a good half chapter of content at that point, and his experiences after being murdered by his boss were, I believe, interesting and even amusing.
Do you think it was a bold surprise to murder my hero in Chapter Five? ;-) Don't worry, he'll be back.