My love is a mer man

Mark fishbach is an apprentice of a famous scientist called w. d. gaster (lol).

Mark was told to never go through the big doors with the caution sign.

And out of curiosity, and determination, Mark disobeys gaster and enters the room. only to find something that was unspeakable through words of his mouth.

he meets Sean or Jack McLoughlin a mer man or the Irish sea.

Mark gets caught by gaster. Gaster tells Mark to leave now but Mark doesn't.

what will happen to mark? and why was Jack there in the first place?

find out in the book if you dare read it!