Blue and friends are getting ready for a big musical, and everyone in the neighborhood is coming. But Tickety, Blue's partner in the act, loses her voice, and we need someone to sing replacing her. Will Steve be able to find all three clues to find out who Blue's new partner is, or is he going to give up?
At the start of the movie, Blue, Mr. Salt and Mrs. Pepper welcome us into the house. They are preparing for a big music show in the backyard and now they can really get ready. There is one character that is missing though, Steve. They can hear him snoring, it seems that he is still in bed sleeping. Mr. Salt says that it is time for Paprika to have breakfast, and leaves with Mrs. Pepper and Paprika. As Steve mumbles in his sleep, Blue and Tickety manage to wake him up by yelling out "Wake up, Steve!!". Steve groggily sits up and he said that the viewer is here really early this morning. Steve realizes that today is the big music show and he has overslept by mistake. Fortunately, he tells them, through song, that if we work fast and hard, we can still be ready in time for the "You Can Be Anything You Want to Be" show, which is about what everyone wants to be when they grow up.
After getting ready, the residents of the Blue's Clues house walk into the kitchen for a big breakfast. Mr. Salt, Mrs. Pepper, and Paprika serve various food such as pancakes, toast, fruit, cereal, and orange juice. While eating, the characters begin a conversation about the big music show. Periwinkle eavesdrops on them, believing them to be talking about a magic show. Afterwards, Periwinkle leaves to rehearse.
Inside, Blue gives Steve a clipboard of things that they need to do to get ready for the big day. having their breakfast is the very first thing, so Steve crosses breakfast off of his list of things to do. The characters talk about what theyare going to be doing in the show. Slippery says he wants to be captain on a boat when he grows up. Shovel and Pail are going to sing about being animal doctors. Mailbox says he plans to sing about being a comedian. Blue and Tickety are going to sing a duet about being teachers. However, while rehearsing, Tickety's voice starts becoming raspy. Steve tells her that she can still be a part of the show by ringing her bells. However, this leaves Blue without a singing partner. Blue was very sad because she does not want to sing all-alone, but Tickety thinks that as long as Blue does not give up, she can go on with a new singing partner.
Blue perks up and agrees and decides that they will play Blue's Clues to figure out who it is. Steve adds it to the checklist. Steve goes to get his notebook from Sidetable, but is called by Mr. Salt, who needs some help in the kitchen. While Steve goes to check on the problem, Sidetable sadly sings to herself about how she wants to be in the show, but is too shy to say anything about it. When Steve returns, Sidetable tries to tell Steve her desires, but gives up and lets Steve take his notebook. Steve tells the viewers at home that he loves songs and he loves making up songs. In fact, he wants to make up a song to sing with them in the big music show, so he adds it to the to do list.
As Steve begins to look for clues outside, he laments to the viewers how he never found a clue without their or anyone's help, and how he would like to try and find one himself before the viewer spotting it. However, the first clue is revealed to be on the notebook, as pointed out by the viewers. Steve compliments their clue finding skills, saying that he wishes he was as good at finding clues as the viewers were.
Surreptitiously, Periwinkle nabs Steve's checklist, hides it under a cape, and shows the viewers a trick where he makes the checklist appear. He then leaves it on a table and goes to look for Steve, who shows up and finds the clipboard. Sidetable tries to talk to Steve again, but Slippery calls him to help out with making hats. The viewers are left alone with Sidetable again and she vows that this time, she is really going to tell Steve that she wants to be in the show.
Meanwhile, Slippery and Steve come in with many hats and start singing a song called Silly Hat. Sidetable tries to talk to Steve again, but her shyness gets the best of her again, causing her to just say she wants to help out in the show. Steve then tells her to hold the hats on her table, which leaves her sad. Several of Steve's friends appear with multiple props, asking him what to do with them. Through song, Steve helps them and they all finish the stage.
Periwinkle shows up yet again, trying to get Steve to view his magic, but Mr. Salt needs Steve's help in the kitchen again. This time Mr. Salt was trying to find the chocolate chips. While Steve was in the kitchen, Periwinkle shows the viewers another magic trick. Periwinkle was going to make a green knob disappear. He does so by moving it behind him with his tail. He then leaves, uncovering a clue on a different knob.
Steve appears and is disappointed that he had not found it himself. There is still one left, though, so he figures that maybe he will find that one. Periwinkle, meanwhile, returns to find that Steve had left. He sadly comments that he is sure Steve would like his tricks, if only he had a chance to show him. After Mr. Salt delivers cookies, Steve checks snacks off the list and then notices that they still need to finish their song.
So, Blue, Steve, and the viewers skidoo into a music sheet. There, Steve meets an anthropomorphic G Clef, who offers to help him write a song. While in the music sheet, Steve learns about notes. Some notes are high, and some notes are low (as shown on a staff). The notes then sing in unison from different pitches about putting the notes together. Steve also learns about rhythm and tempo. Steve then comes up with a song, consisting of the words "beep bop bay". However, he feels his song is incomplete, even with rhythm and tempo. G Clef tells him that music comes from inside. Soon, Steve develops a complete song and now there is only one thing left to do on the checklist, and that is to find the last clue.
As Steve searches around for it, Periwinkle shows up for the third time to show Steve a magic trick. However, just as Periwinkle left to get the trick ready, Steve is called to Tickets and Blue to help Slippery, and walks away. As Periwinkle came back, the viewers tell Periwinkle that Steve left again to help somebody. He complains that with Steve being so busy, he will never get to see his magic tricks. Meanwhile, Slippery is having trouble rehearsing his act. He is afraid he will slip on stage. Steve tells him not to give up, but to go on. After hearing this, Slippery feels better. Upon returning to the real world, Sidetable tries to tell Steve her desires again, but once again fails. Steve then has her collect tickets.
After that, Steve tries to find the third clue himself, with no avail. He begins to think that he might never find it, but his friends tell him in song what he told Slippery; "Don't give up, just go on." Steve returns to finding the clue, and runs into a stack of boxes. A cardboard drawer lands in his hands, which is revealed to be not only the final clue, but Steve's very first clue! As he looks directly at his very first clue, Steve feels very triumphant and victorious. Steve happily gets out his notebook, draws the clue, and runs to the Thinking Chair before the show can start. Impulsively, he focuses on one clue, the notebook, and thinks he is the right answer. But he realizes that he doesn't have a drawer or a knob. After analyzing the clues, Steve and the viewers come to the conclusion that Blue wants Sidetable to be her new partner. Steve goes to tell Sidetable, but then remembers that Sidetable was collecting tickets. So, Steve and his friends look for Sidetable by the end of the fence post.
Once they got there, however, Sidetable's nowhere to be seen, so everybody decides to split up and try to find her. Periwinkle appears again, asking Steve if he will watch his trick. Steve, instead, assigns Periwinkle and the viewers to look for Sidetable together in the backyard. They find her, and it turns out that she was hiding from the others because she believes she is not going to be in the big music show, and she is too shy to ask. She sings her song again, and after Periwinkle compliments her, she becomes happy again and is ready to tell Steve about her desires, yet again. Periwinkle then comes up with an idea to do for a magic trick. Periwinkle tells Sidetable that he will make her appear for everyone to see. He hides her under his cape and yells for everybody to come here. Steve and his friends see Periwinkle and he tells them to say the magic words, "Peri pocus, hocus crocus!". The trick works and Sidetable tells Steve she wants to sing in the music show and Steve tells her that they were looking for her because Blue wants to be her singing partner in the music show.
However, Periwinkle is confused by all of this, as he thought it was a magic show. Everybody tells him that it is not a magic show, it was a music show, where they can do various things, like make up songs, do dances, tell jokes and wisecracks, wear costumes, and sing. This, however, does not make him happy because singing is not his strong suit, magic is. Disappointed, he hides under his cape. Tickety goes to Periwinkle and tells him not to give up and she offers that Periwinkle could do something else in the show. Purple Kangaroo then tells the group that the crowd is getting impatient. However, nobody is ready yet: Mailbox forgot his jokes, Slippery does not have his costume, Sidetable and Blue need more practice, Shovel and Pail search for the animals, and Tickety tells Steve that they need more time. Steve has them go practice, and tells Periwinkle to perform his magic to entertain the audience to keep them busy, while they get ready for the show.
As everyone prepares backstage, the audience is delighted by Periwinkle's tricks, until finally everyone is ready to start the show and he performs his final trick; "Peri pocus, ocus crocus, gotta go-cus." When everybody is ready, Slippery goes onstage, and slips, just like he was worried about. Everybody tells him to not give up and go on. Slippery picks himself up and continues. After Shovel and Pail's doctor act, Mailbox joins in the show with a joke, getting stuck at first, but they help him to get free. After this, Blue and Sidetable both go on and sing. Steve then goes up and sings his song, overcoming his nervousness, and finally everyone joins in for a reprise of the main number. The curtain closes, and opens revealing everyone. They thank the viewers for their help with a group singing the slower, Broadway-style version of the So Long Song. Steve tells everyone, including the viewers, to take a bow, and everyone proceeds to do so, as the movie draws to a close.