The problem is that the image map has an empty href attribute and that causes it to be a link that refreshes the passage (outside of Harlowe’s normal behaviour).
If you remove that attribute, it should work fine. If removing the href causes accessibility issues, you can always put href="javascript:void(0)". It’s also good to wrap the hook around just the map coordinate you want to trigger.
This is a working version, similar to your code example, with 2 clickable areas:
Oh, okay…yeah, I just copied that code from a website that lets you easily generate image maps without really understanding everything there. Works now. Thanks!