Sapphire & Steel - the popular and scary 1970s ITV drama series about two mysterious investigators of temporal anomalies - only ran for a mere six adventures. The final story saw them trapped forever in limbo and viewers were left wondering whatever became of them.
Not a lot of people realise that ATV/ITC actually made a seventh adventure but it was deemed too terrifying for broadcast.
Here's ITC's original trade ad for it.
What do you think...?
"Whatever you do, don't look around you.....!"