...is one of the plot keywords for this film. What's all that about then? (another one is "stabbed in the head". Who searches for films with these criteria? I'm not into films much but I can't resist anything where a non-existent cast member is stabbed in the head and there's skinny dipping)
I wonder how to explain it. I think it's referencing Chuck Conners' son who appeared in a photograph, he plays Slausen's brother. The photo of Slausen, his wife, and brother. The brother, named Davey is in the credits (as Shailar Coby) but there's no actual character or actor playing him in the movie. It's part of the twist of the film. There is no Shailar Coby. They make you think the character is a different person in the credits but it turns out Davey is actually Slausen in disguise, and the brother is actually dead. Chuck Conners plays both of them.
And to answer your question, Tanya Roberts character is the one stabbed in the head with an hatchet.