I have to agree. Her acting was awful. He was great, though. Did you know that he was in the movie version of Poe's The Raven? He was really young.
I looked up "Watcher in the Woods" on Wikipedia. It's not the movie I'm thinking of. Do you mean the OLD version of "The Raven" that had Vincent Price in it?
I love Watcher in the Woods! What I like is that it really isn't a "scary" movie so-to-speak but rather an awesome thriller about the girl and "alien (?)" accidently getting stuck in each others demension (sp?). But, it still keeps me on the edge of my seat even to this day. I found it on ebay a while back and it is one of those movies I can watch many times without getting tired of it.
I found it! I was thinking of "The Moon Spinners", which is based on a Mary Stewart book. It came out in 1964 with Hayley Mills.