Sprocket is not feeling well as he lies in his doggie basket. He is wearing a heating pad on his head and Doc tries a few suggestions to help the dog feel better. In the end Doc decides to take Sprocket to the vet. Sprocket, however, does not want to go.
Wembley is excited about something and runs into his room to tell Gobo, who is reading from one of Traveling Matt's books about the Beast of Blue Rock. Gobo decides to complete the journey to Blue Rock that Matt never finished. He recounts an adventure of Matt's from a former postcard, when Matt had discovered lawnmowers as "garden creatures". Gobo asks Wembley to accompany him on the trip. Wembley is excited at first but then remembers that he and Gobo are supposed to particiapte in Red's Splash-a-Thon as a team. Gobo is adamant about going on the trip, however, and Wembley is then forced to choose: go on Gobo's journey or stay to be in Red's Splash-a-Thon. Gobo, Mokey, Wembley, Boober and Red hold a vote. Mokey votes for Gobo and Boober sticks with Red. Wembley, wanting to please both sides, inadvertantly breaks the tie by sort of accidentally voting for Red, rendering her victorious and she immediately cancels the trip. Gobo is furious with Wembley for his indecisiveness yet again.
Gobo packs for his trip as Wembley comes into their room. He is stunned to see that Gobo is going on the trip anyway despite the vote. They get into an arguement as Gobo blasts Wembley for his constant indecisions and Wembley counter attacks by claiming he has the right to be indecisive. Gobo, hoisting his backpack over his back, begins walking out in a huff, yet Wembley manages to wish him a brief but heartfelt "good luck". Gobo thanks him and leaves, but there is still much tension between them. Later that night, Wembley is lying in bed but is wide awake from his earlier fight with Gobo. He tosses and turns and falls right out of bed. He realizes that he is alone at night for the first time and sings a song about how he is afraid of being alone on his own.
Sprocket is feigning being well as he tries to convince Doc he is not sick to avoid being sent to the vet. Doc doesn't buy the dog's shenanigans, but Sprocket gets even more delirious and starts to fend off Doc.
Next morning, Boober enters Gobo and Wembley's room. He finds the place in a shambles as Wembley snores loudly from his bed. Boober accidentally bumps into Gobo's pickax, which Wembley immediately wakes up and notices Gobo had fogotten to take. Wembley realizes Gobo won't be able to break into Blue Rock without his pickax. At the Trash Heap's, Wembley has informed her of Gobo's trip. The Trash Heap tells Wembley that the journey to Blue Rock is one of the most terrifying in the universe. But Wembley is determined to get Gobo's pickax to him. The Trash Heap starts singing a lively reggae number to relieve Wembley's fears for going, while Wembley, Philo and Gunge perform a limbo while joining in the song.
Armed with the pickax, Wembley sets off for Blue Rock to catch up with Gobo. Boober tries to stop him, but Wembley continues on. Boober informs Mokey and Red about Wembley and they all decide to follow him. They eventually catch up to Wembley, who asks Red about her Splash-a-Thon. She says that he is more important. Wembley is touched and they all set off for Blue Rock. They come upon an ancient Doozer construction bridging a deep chasm. Wembley crosses it to get them some of the construction parts for lunch, but the structure begins to collapse into the chasm with Wembley sitting on top of it. The others watch in horror as Wembley is catapulted to the opposite side of the chasm by the destruction of the Doozer bridge, completely separating him from the others. They tell him to wait, but he is more determined than ever to get to Gobo and runs off further into the tunnels. He eventually finds Blue Rock and fears he also finds the beast due to seeing a creepy shadow moving toward him. He cowers against a wall.
Doc is still fighting with Sprocket over going to the vet. When the pooch finally gets so weak he almost passes out, Doc finally convinces Sprocket to go and face his fears. Sprocket relents and they go.
Wembley and Gobo accidentally run into each other near Blue Rock. Gobo is delighted and touched that Wembley has brought him his pickax, but seems to have reservations about breaking into Blue Rock. He is overwhelmed at Wembley's bravery, however. Wembley is excited to watch his best friend break into Blue Rock. But Gobo admits he is scared and wants to leave. Wembley is shocked, but is a little relieved as it seems Gobo is 'wembling'. They start a country-duet about 'wembling' to calm themselves. Afterward, it hasn't worked for Gobo. Wembley grabs the pickax and slams it into Blue Rock to give Gobo encouragement. He is unsuccessful. Gobo helps him, and this time they both fall through Blue Rock's walls to the inside. Once inside, they look around and see a large image of the Trash Heap before them. She is obviously watching them via magic and congratulates the boys on their journey completion. She informs them that the real beast of Blue Rock is fear itself, and that they conquered it by facing their fears. She magically transports them back home, where they land in the Fraggle pool, accidentally winning Red's Splash-a-Thon in the process.
Doc and Sprocket return from the vet's. Doc says he's proud that Sprocket seems to be over his fears, and Sprocket expresses his newfound bravery about the vet - until Doc informs him it's time to take his medicine!