The woman handed Emily a small bottle. "This potion will allow you to transform into a mermaid."
Emily took the bottle, looking at it in her hands as if it couldn't be real.
"How does it work?" she asked.
"Drink half the vial. After that, whenever you immerse yourself in saltwater you will become a mermaid. The ocean is of course the best, but add enough salt to a full bathtub and it will change you as well. Drinking saltwater will also cause you to change."
"For how long?"
"Until you dry off."
"Why only saltwater?"
"My dear, think of the risks. You wouldn't want to be suddenly transform by spilling a glass of water or getting caught in a sudden downpour would you?"
"No, that makes sense. You said to drink half. Does that mean I can change twice?"
"Once you take half the potion and transform for the first time, you will continue to tranform from contact with saltwater. That is, as long as you do not go 24 hours without it. If you do, the effects of the potion will expire."
"So why do I need the other half of the bottle?"
"Perhaps circumstances will keep you apart from saltwater for 24 hours and you will wish to change again; it gives you a second chance. But if you are careful, you will not need it for that. Instead, you may meet another whom wishes to join you as a mer."
Emily's mind reeled. Her lifelong dreams, previously impossible. "Thank you."