unanswered question

• mysterySomething unexplained or unknown
• puzzleChallenge testing ingenuity
• riddlePuzzling question to solve
• enigmaSomething hard to fathom
• silenceTotal lack of sound

doubt · uncertainty · lingering · haunting · unresolved · pending · hanging · curiosity · wondering · searching · void · gap · blank · inquiry · quest · unknown · nagging · frustration

• awkward silences
• unfinished obligationsunfinished business, overdue payment, missed deadline
• story openersopening line, opening lines, first line, first chapter, chapter one