dangler

a plot or character element that is introduced but never fully explained or resolved, leaving the audience with unanswered questions or loose ends

A dangler is a plot element or character that is introduced in a story but never fully explained or resolved. It creates unanswered questions or loose ends, leaving the audience curious or confused about its significance. For instance, if a novel mentions a mysterious letter but never addresses its contents or importance, that letter acts as a dangler.