The Narwhal Problem (Mermaid Tales, Bk. 19)

All the merkids are super-excited! Two famous narwhal scientists are visiting Trident City with their daughter, Nadine. Best of all, someone is going to get to show Nadine around the city while her parents are in meetings! But who? All the merkids want to be the one, so how are they going to decide who gets to do it?

Mrs. Karp, their teacher, decides to organize a code-breaking contest, but with the competition getting fierce, it is more like a code war! Even Kiki, Echo, and Shelly are fighting! Is there a way that everyone can win?