The example I was thinking of was an early episode of Farscape where a murder occurs onboard the ship, there are at least three strong suspects including two main characters. At the end of the episode it is still unclear exactly who the killer was, and it is never brought up again(except as a way to add tension to the crew).
Is there a word for this?
Wanted to make clear too its not a mystery the writers have decided to drop, but one they have intentionally make ambiguous.
As an example, Homicide: Life on the Street had an ongoing plot about the murder of Adena Watson. It was the first case Tim Bayless took, and was never resolved. At times, Bayless would go back to it, or it would be referred to, but it was never resolved and the show ended without ever finding the killer.
I don’t know if there’s a name for it, since it’s not very common to deliberately leave things ambiguous over a long run of a series (other than when the series is cancelled without a resolution). As the series goes on, the impulse to tie up the loose ends usually wins out, especially as the writers start getting stuck for story ideas.