Austin rubbed his eyes in disbelief as the creature wearing Anna's face beached itself on the sand.
There was no mistaking that fishtail. She was a mermaid. A gorgeous mermaid with bigger boobs than Anna's, hidden behind a pair of starfish that seemed to be suction-cupped on. The merman also pulled himself onto the shore, handed the mermaid the bag in his hand, and then looked around warily before whispering something to the mermaid. (Apparently, he hadn't yet spied Austin.) As Austin made his way down to the very edge of the water, he saw "Anna" whisper something back, and then the two kissed tenderly on the lips, and the merman gave another anxious look around before hastily crawled back to the water.
Austin was now close enough to peek around some large rocks and actually get a good look at this creature. Was it a trick? An illusion? Only, it was definitely her face. Definitely Anna's, there was no question about it. He stepped out into the open, the beach-sand shifting under his feet. "Anna…?"
The mermaid jumped, clutching the bag close. Then her eyes went wide. "Austin!? What—how!?"
"I've been looking for you, all this time! Anna, you're—you're—a mermaid!"
"I got changed," she said simply.
"How?"
"It was accident," she said. "That merman who was here a second ago? I met him on this beach, and I changed, and we fell in love."
Austin didn't really know what to make of that, or how to respond. His sister was in love with a merman? How does that even work? His thoughts were interrupted by a very masculine roar—
"GRRAAAWR, get away from her, filthy human!!!" Eric came flopping up onto the beach, dragging his tail and his trident behind him as best he could manage, which was to say, not very gracefully at all.
"Eric, no, stop!" cried Anna. "This is Austin! He's my brother!!!"
"Your… brother?"
"He's been looking for me!" said Anna. "Of course he has, because I disappeared without a trace! This is why I need to see my family!"
Eric stopped, glared at the newcomer, then said softly to Anna, "But; if this is your brother, surely that means that he can tell your family you're all right? Then you don't have to risk being discovered!"
"Eric, I have to!"
"It's dangerous—"
Anna put her hands on her hips. "I'm going, and that's final."
Eric sighed, but then Anna leaned in close again, kissed him just underneath the ear, and whispered so that Austin couldn't hear, "But I will come back to you. After all, I might be a mom!"
Eric couldn't help but smile at that. "All right," he said. "I'll let you go. But be careful. Tell no one but your family the truth."
"I won't." Then Anna turned to her brother and said to him, "Austin, you need to take what's in this bag. You need to go, and get me a really long dress to wear, and a pair of crutches, and some way to attach these two objects to the crutch-handles."
Austin was very confused, but he took the bag and looked inside. "You need a dress…?"
"To hide my tail," said Anna. "I can't change back."
"…And crutches," Austin went on, fishing the rock and the coin out of the bag. "With these attached somehow."
"They're magic," said Anna. "They'll let me get around."
"If you say so," said Austin. He still wasn't sure that any of this was real. It could be, this mermaid was just an empty illusion, a vision with no substance. Or it could be a malevolent creature who had stolen his sister's face and needed a way onto land. But she seemed so much like the real Anna… "Anna, let me ask you something. Are you the only person who got—changed like this?"
Anna shook her head. "No. There's another one, a guy named Aaron. He got turned into a merman weeks and weeks ago. He's got a mermaid who loves him down there, but I don't think he likes having a tail very much."
"Oh? Why not?"
Anna blushed. In fact, she was getting very flushed now, and her brow was dripping with sweat. "Because… because, ah…" Anna let out a little gasp and closed her eyes, trying to keep it together. These starfish stuck on her boobs were the only modesty she had right now, but boy were they ever taking their toll.
"Anna, are you okay!?"
"Just, uh… just hurry, all right? I'll be here when you get back. I love you, brother." With that, she slipped into the water after Eric, and both merpeople disappeared, leaving a very dumbfounded young man standing on the uncanny beach.