Just because I've never really come across a complete list of summaries of X-1 episodes I thought I'd use this space to catalog them because while as of this writing there are only 9 episodes (edited post, you see) we've done like a third of them which would make this the most complete catalog I know of. So...here goes.
The seventh expedition to the 'Galactic Barrier' between Earth and the mysterious Volta where the previous six missions have vanished. Is it radiation or something even more sinister? Establishing almost every trope of space travel science fiction this felt ultimately like the baseline episode, 5s all around.