The Poison Waves (Secrets of the Sky #2)

Kiya and Kinjal have succeeded in their first quest in the magical world of the Kingdom Beyond, but it quickly becomes obvious that whatever good they achieved might not be enough. Their faithful flying horses Snowy and Raat reappear and whisk them back to the Kingdom at the behest of the magical Princess Pakkhiraj. There, she tells them the water pari--winged merpeople--are slowly being poisoned and it is up to the twins to figure it out and put a stop to it.

Fortunately, Kiya has the know-how to solve this mystery...if only she can put the pieces together before the evil serpent king, Sesha, knows they've reentered the Kingdom!