Did you also watch Journey to the Unknown as well? That was five years earlier and it has a really creepy theme as well (someone whistling from an empty amusement park at night.) It was a joint US-Hammer production. I enjoy seeing all the old American television stars from the 60s and 70s in both Journey to the Unknown and Thriller, and some British stars who were famous at the time in the US like Judy Carne and Susan Hampshire.