The OA was a sci-fi mystery series that began airing back in 2016, following Brit Marling’s Prairie Johnson, a young woman who suddenly and miraculously appears after having been missing for over seven years. In addition to returning from her presumed dead status, Johnson can see for the first time, having mysteriously cured her blindness. The series was created and executive produced by Brit Marling in collaboration with Zal Batmanglij, with Batmanglij directing all 16 episodes.

The OA is one of the most heartbreaking entries on this list, as Netflix unceremoniously canceled it on a cliffhanger ending. According to Johnson and Batmanglij, the series did have a planned ending, leaving Netflix’s decision baffling to audiences, many of whom initially believed the cancelation announcement was some meta-marketing ploy. Despite the cliffhanger ending, the series is still regarded as one of the best sci-fi shows of its day, though the question of whether the series will ever get a satisfying conclusion remains to be seen.