Kevin was growing board and about ready to head back to Lilia's apartment when he saw a familiar car park nearby. He watched Gisela, in her human male form walk to the room, swipe her access card, and enter. Kevin rushed to the door and managed to just barely prevent it from closing. He burst into the motel room and slammed the door behind him.
Gisela wheeled around. "You!" Then Gisela's eye's went wide. "WHAT HAVE YOU DONE?!"
"I escaped" sneered Kevin.
"Where is the necklace?" asked Gisela. "How did you return to normal?"
"Other ways."
"You fool! The necklace and my kiss are magical. You've messed everything up! I...I may be stuck like this now..."
"Serves you right."
Gisela let out an angry scream and charged Kevin, slamming him against the door. The two tumbled to the floor, grappling with each other. Neither had any wrestling training so the fight had all the technical proficiency of two children in a schoolyard. A table toppled over as the two awkwardly struggled.
Kevin finally broke free and pulled himself to his feet, but felt woozy. Gisela hadn't struck him in the head yet his legs felt weak. Kevin managed a couple steps before his feet went out from under him and he collapsed back onto the floor. The sound of ribbing fabric followed. Kevin looked at his legs to find his shorts were tearing as his legs reformed into a tail. Lilia's serum was wearing off and it had been far less than 24 hours - maybe only 12. Kevin felt his chest heaving and expanding. He pulled off the shirt that was now all too tight. The serum's effects had completely worn off and he was a mermaid again.
Gisela looked at mermaid Kevin sprawled on the motel floor. Now Gisela could kiss Kevin and get her mermaid form back...but then she would be at his mercy - assuming Kevin's temporary change hadn't ruined the magic. Or Gisela could force Kevin to finally reveal Lilia's location.