Revealing mistake: The seam of the mermaid's fin suit is visible as she twists and turns towards the boat's gunwhale.
Night Gallery (1970)
1 revealing mistake in Lindemann's Catch - chronological order
Starring: Joanna Pettet, Rod Serling, Larry Watson, Matt Pelto
The Cemetery - S1-E1
Continuity mistake: From the inside view of the window the Hendricks gravestone and the family name is visible on it. From the outside view of the window the gravestone and the Hendricks are facing away from the window.
Rod Serling: For those of you who've never met me, you might call me the under-nourished Alfred Hitchcock.
Trivia: The scene of the spooky castle on the rocky shore was used in episodes of "Gilligan's Island" featuring Vito Scotti as mad scientist Boris Balinkoff.