Merle and Zora - The Blackmailer Part 3 of 6

Zora is the assistant from Mike Baumann, the head of a research institute. One evening she works alone in the office. She is attacked by a strange woman. Zora is quickly defenseless by shackles and gags. After all, the stranger leaves her like this.

Weeks later, Mike introduces her to a new intern, Merle. Zora is terrified inwardly. She knows Merle's voice from the robbery. What is being played here?