Hover image behind

Hello,

As you can see on my website when you hover over 'coffee stories' the word 'shell' appears. For some reason this appears underneath my thumbnail image but instead I would like it to replace the image. How can I do this?

Is there a way to make the original image disappear on hover at all?

I want to do this with all the thumbnails but have just started with one.

Thanks,

https://greyhound-keyboard-sa3k.squarespace.com/