Nancy, Bess, and George are off to Ireland for a bike tour, despite the fact that every single book makes it seem like Bess is too fat to walk around the block let alone cycle up and down hills. Since she's a detective, Nancy can't help noticing a guy with a missing pinkie finger getting off a flight from Australia. They then meet Bob, the leader of their tour group. He introduces them to all the others, including Natalie and her husband, Jim, from California, a college professor named Carl, and two Australian girls: Rhonda and Rachel. Nancy notices that Rhonda freaks out when they leave the airport after seeing some guy, but the girl calms down pretty fast.
Bob then takes them to their first stop and where they'll spend the night. He introduces them to Derek and Camilla, two more riders and lays down the rules. Basically, everyone can ride at their own pace. Groups will get cell phones to stay in touch, but some people will ride more every day than others. That doesn't sound safe to me at all but whatever.
The very first night, Rhonda passes out while talking with Derek. He points out that she was drinking a soda that was meant for Rachel, but Carl then knocks it over before anyone can check on it. Nancy sees Derek trying to take a photo of the passed out girl and then sees him whispering into a tape recorder. Bess refuses to believe that he might be guilty of anything because he's just too damn cute. Derek then disappears when they get together for dinner.
Nancy decides to follow Rachel the next day and ride with her, while Bess goes with Derek and George goes with Rhonda. Rachel refuses to talk during the ride because she wants to focus. When they take a short break, Nancy heads off and discovers that someone slashed her tire. She has to wait for help as Rachel rides off without her.
When the group meets up later that night for dinner, Nancy hears something outside and discovers Rachel passed out on the ground. The pub sign fell and hit her on the head. Nancy finds a note from “D” to “R” asking her to come outside, and Jim finds that someone actually cut the sign to make it fall. This leads Nancy to tell Rachel that she's a detective and offering to help. Rachel turns her down flat and points out that it was just an accident. Nancy then sees Rhonda talking to a shadowy guy in black.
When they start off the next day, George plans to follow Rachel but almost gets hit by the tour group van. Terry, the driver, claims he didn't see her and spends so much time being irritating about the whole thing that Rachel takes off with her sister. Each time the girls almost catch up to them, they take off even faster. The sisters even unlock a gate and let out a bunch of sheep that block their path.
They finally do catch up to them, just in time to see a blue sedan barrel right into Rhonda. Terry shows up with the van to take her to the hospital and quickly claims that he doesn't have room for anyone else. Rachel is unnerved enough that she spends the rest of the day with Nancy. They wind up doing some souvenir shopping, and Nancy sees the guy with the missing finger. She hears him talking with an Australian accent about how his family came from the region. George follows him outside and sees him get into a blue sedan, just like the one that hit Rhonda.
Rhonda turns out to be fine and ready to do some more biking the next day. Nancy makes up an excuse to get inside her room and snoop around, but then Derek wanders in with an excuse about thinking it was his room and how he left his charging cable there. It turns into a standoff that only ends when Nancy pretends like she was doing Rhonda a favor and leaves with him.
Some of the gang heads to this beautiful mountain park area to check out the sights. Nancy is having fun right up until a large piece of rock comes crashing down on her head. Terry and Bob rush over to make sure she's okay and to help her sit down and rest. She can't help remembering that Derek was in the vicinity right before it happened. When she looks at him though, he just looks away.
George sneaks around, finds that the sisters had a British tabloid, and learns that Derek writes for the paper. Nancy approaches Camilla to ask what happened to Derek and finds out that he took off. He left a note that he got his story and was heading back to London. It turns out that the sisters are the daughters of some huge publishing tycoon. He bought a bunch of British papers and actually fired Derek, so Derek went crazy to try and find dirt on his daughters to make him look stupid or something.
The group starts off for the day and wind up in an area where the water washes out the road late in the day. Rhonda shows up to tell them that Rachel broke down on the side of the road and needs help. Jim freaks out when he learns that she left her sister there without a cell phone, but Nancy offers to ride back and check on her. She instead finds the tour group van upside down on the side of the road with footprints leading in the wrong direction. To make things worse, Nancy takes too long to check things out and finds the water rushing in at a fast pace.
Nancy manages to escape by ditching her bike and wading through the water. When she gets back to the group and tells them what happened, Rhonda breaks down. She actually faked her own bike breaking to get Derek alone, not knowing that he was already gone, and she last saw Rachel riding off alone. She also reveals that the dude with the missing pinkie is Smithson, her and her sister's former bodyguard. They begged their dad to let them travel alone, but the guy showed up anyway. Rhonda agrees to call her dad to see if he sent him and learns that Smithson called in, claiming he kidnapped her sister and wanted a ransom.
Their dad makes one phone call and has the cops there in no time. They find Terry and discover that he skipped out to watch a soccer match in the pub and left his cell phone in the van. When he had the accident, he just ran because he was worried about losing his job. The cops find Smithson's car, which conveniently has Rachel's bike in the trunk. Nancy then remembers hearing him talk about the manor house where his family once lived and convinces the cops to check it out. Smithson then comes out and says he'll kill Rachel if they come after him.
While the cops distract him, Nancy sneaks up behind him. The cops run at him as she karate chops his gun out of his hands. Hey, it's been awhile since Nancy karate chopped anyone! The girls' dad then shows up to make sure they're okay, and as he takes parenting lessons from George Fowler, he promises to put them first from now on. The cops arrest Smithson and keep him in custody. They find that Derek wrote a story about step dancing because he didn't have the heart to slander the girls, and Rhonda asks her dad to help him find a better job. And in the end, Rachel asks Nancy if she wants a job as her new bodyguard.
*Bess apparently buys new luggage every year as the trends change, which seems like a massive waste to me. What do I know though? I usually travel with reusable shopping bags lol.
*Bob introduces Carl as a college professor, but Carl then says he's just as assistant chemistry professor and thanks him for the upgrade. Say what now? Even if he's an assistant professor, he's still a professor!
*Rachel gets a clean bill of health from a local doctor and permission to ride the next day. What the hell? She literally had a heavy ass wood sign fall several feet and smack her in the head to the point where she passed out!
*Derek was the one who threw the rock at Nancy's head earlier in the book. Camilla says that he did it to throw her off his tail. And yet, the dude is supposedly such a softie that he can't write a bad word about anyone.
*Terry gets a concussion from the van accident and winds up in the hospital overnight. Everyone else is totally fine after getting knocked in the head though.
*Smithson worked for a group of people unhappy with their dad's business decisions, which seems really odd to me.