At first you weren't aware of the change, only felt some tingling in your legs. But soon, your legs started to fuse together, their skin becoming similar to Ondin's tail.
You were about to scream in terror, when you felt like a sea-urchin lodged itself in your throat.
- – — – -
You weren't the only one to be denied sleep. Ondine couldn't even start her paperwork, because upon entering her office she discovering her King, patiently waiting for her.
Wile merfolks are magical beings build to live underwater, for some unknown reason they vocal cords are still very similar to human one, thus only working properly wile breathing air. (Except in the sirens' case, hence their ability to use echolocation.) That's why their ‘sea-speach’ is very similar to our sing language. Which is why the King was signing to speak with your wife.
«I believe congratulations are in order, adjutant Neptune.» the King asked, a large smile on her face. «Can I ask why you aren't at your husband's side?»
Ondine forced herself to look the older mermaid eyes in eyes, before answering «Because of my work. I have duties towards peoples, I can't simply abandon my post wherever I want!»
The King's face darkened at this, betraying her sadness. «But bonding with someone mean having duties toward each others, duties that should pass before any others. Never make your work pass before your family adjutant, or someday your life will become nothing more than a pile of regret and sorrow.» She looked like someone speaking from experience.
Then, after a sigh escaped her mouth, the royal mermaid added «My main reason for being here was Natalie's promotion to junior seamaid, I wanted to announce it myself.» Before adding «But now I really want to meet your husband, so you know what? As soon as junior seamaid Wave is aware of her new rank, you and me are going to the surface, meeting that human of yours!»
But as soon as the two mermaids swam out of Ondine's office, your wife received a message you accidentally sent via your link. It wasn't a message made of words, but of pain. A pain that was familiar to Ondine, like having a sea-urchin lodged itself in your throat, that every sirens felt the day their powers manifested for the first time.
Seeing the sudden look of panic on the adjutant's face, the King was about to ask what was wrong, but got her answer even before she could. «He's changing, becoming a siren!»