Loony Lips Lesson 20 Error

I’m getting an “Invalid index set” error in the Loony Lips Lesson 20 (3.1 Godot) when i try to run the program. I’ve been following along and making the changes up to 11:58 in the course video. Retracing my steps hasn’t turned up any errors that I can find.

My program keeps complaining that current_story is Null and won’t run past line 32 in debug mode

(and yes, that “prompt” is “prompts”; I did not adjust the window over enough to show the s on the end)

Any ideas what could be causing it? I’ve also tried deleting and recreating the StoryBook node and its children, however making new ones Godot seems to remember the deleted scripts and naming schema…