Nancy, Bess, and George are off to Emerson College for the weekend to see Ned and experience the annual Winter Carnival. He got a friend, Susan, to let them stay in her dorm room, and he even arranged dates for George and Bess with his friends Jerry and Rob. Susan seems find with them until she finds out they know Rob and suddenly seems less friendly. She later apologizes and says it's fine if they hang out with him.
They do a bunch of fun and random things like start making ice sculptures for an upcoming contest, take a walk across the campus, and have a snowball fight. Nancy notices the oars on Rob's jacket and comments on them, which makes him go from friendly to ice cold. Ned later explains that Rob was the star of the crew team until his grades dropped and the college suspended him.
One of the big events on campus is an exhibit in its art museum of historic jewels. Bess goes crazy, and Rob jokingly says he would steal from her. Nancy keeps noticing how the security guard follows them around. They also listen to a speech from William Whorf, who is some big deal historic jewel collector.
The next day, they all go to a dedication ceremony for some new practice space for the award winning crew team. The coach gives a special shout out to Rob, who unexpectedly disappeared. In the middle of the ceremony, a fire breaks out. Rob shows up later with claims that the ceremony upset him so he went for a run, and he claims he left his jacket inside.
Our big mystery in this book is that someone steals some of the jewels from the collection. Later, the cops show up and take Rob down to the station for questioning in the theft. Nancy previously solved a few mysteries on campus and asks the dean for some time to clear Rob's name to which he agrees. She then finds that someone destroyed a bunch of the sculptures and also finds Rob's jacket close to where the fire broke out.
Turns out the cops showed up and when they catch Nancy with the coat, they take her in for questioning. It doesn't help that the coat is covered in gasoline, which was the accelerate used in the fire. The cops release her after taking to the dean but make it clear that she's just a kid and should stay out of the official investigation. Nancy vows that she'll help Rob though and tells him that when she sees him at the station.
In the hopes of finding the original gas, she breaks away from the group, breaks into a maintenance building, and finds gasoline as well as a label from the missing jewelry. The sergeant not only ignores her but doesn't even really want to send someone to check it out. She also manages to overhear Whorf acting all suspicious like and begins wondering if he was behind the theft and set up Rob so no one would find out.
While hanging out, they all have a run in with Susan and her new boyfriend Greg. Greg picks a fight with Rob for no real reason and attempts to punch him before she drags him off. Rob explains to them that he and Susan dated for a full year and even talked about getting engaged before he broke it off. He also mentions that she was pretty upset he dumped her before she could dump him.
Since all work and no play makes Nancy a dull girl, she takes time out of her busy schedule to go ice skating with the gang. That might be fun if not for the fact that the ice breaks underneath her. Ned gets to her just in time, and they find out that someone removed all the signs and blockades from the thin ice section of the lake. To make matters worse, Rob sends a message to Nancy that the cops have a search warrant for his room. Nancy gets there just as the cops find one of the missing earrings.
Nancy asks to see the earring and points out that it has a Made in China label on the back and isn't an antique. The sergeant seems peeved that he can't arrest Rob and tries to storm off. When she gives him the label she found, he just puts it in his pocket and leaves. That's some nice police work there, guys. Rob tries to get them to just leave him alone, but Nancy convinces him to go skiing to take his mind off things.
They see Susan and Greg again, and when Greg gives him murder eyes, Rob wonders if he's the one behind everything. He even points out that Grey probably started the fight as a way to get close to him and stick the fake earring on him. They head up on the ski lift together, but when Nancy hops off, she finds that someone tampered with her ski. She just narrowly stops in time to avoid serious injury.
While us mere mortal would probably give up at this point, the group goes to the big Winter Carnival dance together. Nancy sees Whorf give something to Greg, which turns out to be a party invitation, but she then realizes that she saw Whorf with someone who looked suspiciously like Susan's dad before. The girls go back to their room and find that Susan hid the photo of her dad that she had out before, but they find another picture in her dresser of her dad with Whorf. They also find a bracelet that matches the fake earring the police found.
Ned and Nancy set up a trap at the sculpture contest. As a judge, Ned announces that they need to check each sculpture for illegal framing, which he uses as an excuse to poke around in Susan's sculpture. Though he doesn't find anything, she does sneak over to Bess' sculpture and knock it over. Nancy holds her down while the police rush over to stop the crazy girl with her knee on another girl's back, only to find Susan holding all the missing jewels.
In the end, we learn that she took the fall for everything and denied that she had any help. Nancy still believes Whorf was in on it and that he probably planned to pay her off. Ned gets her alone and presents her with a necklace that matches the bracelet and earrings, which leads to her kissing him and thanking him for the best Winter Carnival ever. Hey! Nancy got through a whole 147 pages without cheating on her boyfriend, that's some serious progress!
*Ned gets really quiet when describing Rob, and Susan then freaks out. I'm pretty sure I'd think twice about dating him, but Bess is cool with it because he's cute.
*Need another reason to love Ned? He grabs Nancy and plants one on her before telling her that kissing her is his favorite way to warm up.
*Jerry does a good job of both flirting with George and flirting with Bess without really making it clear if he likes one more than the other.
*The official colors for Emerson College are purple and orange, which sound weird and a little gross to me.
*When the whole gang goes out for a fancy dinner, they all make fun of Bess for wanting dessert except for Jerry. He tries to convince them all to try at least one, but Nancy and George claim it's too many calories. That really annoys me.
*It turns out that Ned is a terrible matchmaker. Bess and Jeff go crazy for each other in the end, while Rob invites George to come back and visit him in the spring for some rowing lessons.
*The main suspects listed in the front were stupid. Greg is in like two scenes before the end, Whorf is in maybe three, and we know from the very beginning that Rob had nothing to do with the theft.
*Setting a building on fire is one weird way to draw attention away from a jewelry heist...