Does anyone else wish there were more Mer! Riddle fics? But like instead of one of the Octatrio finding out his secret, it's SOMEONE ELSE? Like- imagine Rook going about his day stalking people as usual, when he suddenly spots Riddle lurking about suspiciously in the woods.
So what does he do? Why the only natural course of action would be to investigate of course! So low and behold, does he find himself face to face with Riddle letting his tail or whatever merform out to breath in a nearby body of water hidden deep within the forest.
Mind you, Riddle didn't realize Rook was spying on him and Jade during P.E, it was Jade who actually noticed him. So there's no way Riddle would ever realize he was being watched in that moment. Thus, Riddle's finally in his element for once and Rook's been rendered completely awestruck that quickly changes into interest.
Bonus points if Riddle's merform's actually a really rare species that he so happened to inherit from his greatgrandparents or some other distant relative despite the human blood in his veins. The chances were low but unfortunately for Mrs. Rosehearts, never zero..