Mystery mouth's voice is Nancy's first clue! Nancy has a new set of hot green walkie-talkies to use in busy places like the mail. But when Bess and George try them out, one of the walkie-talkies disappears. Nancy thinks a bratty boy they know may have taken it. Then Mystery Mouth starts sending Nancy messages on the remaining walkie-talkie. Each message contains a clue. Soon Nancy and her friends are on a crazy chase all over town. Mystery Mouth is talking, but it's Nancy who's doing the walking -- to find out who walked off with the walkie-talkie!

When Bess and George try out Nancy's new walkie-talkies, one of the devices disappears, and a voice calling itself "Mystery Mouth" starts sending clues on the remaining instrument.

River Heights is getting a carousel! And the town is having a special ceremony to unveil it. Nancy, Bess, and George are dizzy with excitement for their first ride on the beautiful antique horses. All the kids who ride the carousel can also try to grab a brass ring that hangs on a pole next to the carousel. Whoever captures the ring wins a special prize! But suddenly the brass ring is gone, and without it the contest will be ruined. Nancy is on the case, but her head is swirling with too many clues. Can she solve this carousel mystery before it spins out of control?

It’s volunteer week at Carl Sandburg Elementary School, and Nancy is very excited about her job. She will be walking Mrs. Rutledge’s dog, Baby. Mrs. Rutledge owns the biggest, fanciest house in River Heights. And she also owns the smallest one—a beautiful antique dollhouse. Nancy loves the tiny furniture and little windows of the dollhouse almost as much as she loves walking Baby. But one day, five pieces of doll furniture are missing, and Mrs. Rutledge thinks Nancy took them! But Nancy is a detective, not a thief...right? Nancy must use her very best detective skills to get herself out of trouble!

Traveling to the site of a commercial shoot, where her model friend Cindy will star, Nancy is alarmed by Cindy’s disappearance and launches an investigation that takes her into the shady side of teen fashion.

While vacationing at a lake, Nancy, Bess, and George have their eyes on first prize in the annual sand castle contest. They use special colored sand and carefully build the castle to look like the ones they researched at the library. If the girls win, they’ll get their picture in the local paper and all the ice cream they can eat. But before judging begins, someone wrecks the girls’ castle and writes a mean message in the sand. Nancy and her friends will have to dig deep to get back into the contest before it’s too late!

Nancy and her friends are on a fun-filled trip to the coast of Maine. But when they find out that the historic town lighthouse might be haunted, the girls are spooked! And when they find mysterious clues that seem to lead them on a treasure hunt, Nancy knows she has a mystery on her hands. Who wrote the clues? And where could they lead? Maybe this lighthouse really is haunted like everyone thinks. One thing’s for sure—it’s up to Nancy to shed some light on this case before they are all left in the dark!

At Camp Treehouse, Nancy’s bunkmate Lauren is having a crummy time, because someone has stolen her camera. Nancy investigates, follows the clues, and helps her new friend.

Nancy has just two days to help her friend and save the ballet! Nancy and her friends are practicing for the big ballet recital. They're so excited, and nervous too. Especially Bess, who can't seem to learn the steps. But then the special music goes missing and the recital might be canceled. Everyone blames Bess and Nancy must take the case!

Nancy’s friends are sad because the class hamster has gone missing. Poor Nibbles. But then Katie brings in a bunny named Bun Franklin to be the new class pet! Everyone is thrilled, and now they can began preparing for the Spring Fair. But soon enough someone starts wrecking the class’s Spring Fair projects, and everyone thinks it must be Bun Franklin! Mrs. Reynolds is afraid he can’t stay. But Nancy is sure it’s not Bun—how can she prove it? It takes a lot of clue hunting and sleuthing for Nancy to realize that what she’s uncovered just may solve two mysteries at once!