Did you figure out who the killer was?
Boris Karloff was too obvious, I knew it had to be someone else. After watching it again, I realized that it was easy to guess that Melton was the killer because:
- he repeatedly accused Costello of being the killer to take the heat off himself
- the stocky figure in the cave matched his body form
- as the hotel manager, he could easily get around and kill people, plant bodies, etc.