It is the fifty-seventh episode in the series.
A mix-up in Echo Canyon causes Happy and Grim to switch voices, leaving the 7D and the King of the Echoes to fix the mix-up and save Queen Delightful.
Happy sings loudly inside the 7D's cottage as a call to wake the others up. However, this really annoys Grumpy, even when the 7D are having breakfast. Grumpy gets so angry that he goes kablooey (familiar to the action Grumpy shows in the title sequence). Even though he's done that, Happy still keeps on doing so; thus, Grumpy and Happy make a bet that if Happy doesn't sing a single note this time tomorrow, Grumpy will make him a thousand pancakes.
Happy confesses that he never won a bet from Grumpy but suddenly he finds out a solution as he remembers what happened the day before: At the queen's castle, as Starchy is listening to the radio, Happy comes in and sings. Starchy tells him to keep quiet to listen to the Tin Can Radio Hour, which shows Howie Hoozer taking the audiences to a journey to the Echo Canyon. This is where the king of the echoes will take your echo and return it back to you if you holler your voice into it. So then Happy comes to the canyon and temporarily gives away his voice for the king to keep it safe and soundless. Now Happy is temporarily mute.
Then he comes back to the cottage. Grumpy firstly thinks he would sing but actually he doesn't, so after that he keeps enjoying the silence. On the next day, Happy is shown writing down his favorite kinds of pancakes as a "pancake wish list". Grumpy can't let the silent Happy win the bet so he tries to make Happy sing by asking him the last line of a song's lyrics and asking him to sing to a puppy that never once hears a happy song. But both schemes get ruined by Sleepy who finishes the last line and Dopey who makes the puppy laugh by making funny expressions. As Doc finishes counting the last seconds, Grumpy loses the bet and bets that Happy's dying to sing about this. However, when Happy intends to do so, he realizes that he's still mute, and runs to the Echo Canyon to find back his voice. The rest of the dwarves think this is somehow fishy so they follow Happy.
As Happy is rushing, he comes across Grim who now possesses his voice. Happy thinks that voice was just familiar to him, not totally, so he doesn't mind that much. Meanwhile, Giselle - Grumpy's goat - is seen finding traces of Happy's scent. At the same time, Grumpy reveals that Giselle was raised by bloodhounds. After that, there's Dopey who does the same thing as Gizelle and Doc shows that Dopey was raised by Gizelle. They have finally found Happy standing on the edge of Echo Canyon and also know why Happy stopped singing. Then, the king of the echoes flies over the 7D and tells them that Happy voice was accidentally given to a wrong person by his newly-recruited nit-witty pixies, Whoopsy and Daisy. But not just Happy, many people got the wrong voices as well. Since Grim is shown speaking with Happy's voice, after the pixies return the voice to Happy, it's Grim's instead.
Hildy makes full use of this opportunity by having Grim talk to Queen Delightful through Happy's voice, that they've got a surprise for Queen Delightful at the Echo Canyon but she has to be blindfolded. Starchy partly ignores what the queen is being told of.
Cut back to Starchy who is enjoying his sandwiches while listening to the Tin Can Radio Hour. The 7D come at him and ask him where Queen Delightful could have possibly gone. By just his poor memory, Starchy leads Bashful, Sneezy, Doc, Sleepy and Dopey to the wrong place. After hearing the word "Echo Canyon" said on the radio, he finally remembers and tells Grumpy and Happy to go there. At the canyon, the queen is seen walking towards the edge of the canyon blindfolded as Grim with fake Happy's voice is telling her to go on. Happy tries to stop by using the voice but since that's Grim's, it's useless. Luckily, the king of the echoes while catching the voices of Happy, Grim and Hildy, he spots the queen and catches her, as well as returns the voices to the correct person, except for Grim and Hildy, where their voices were switched.
The two come back to the cottage but finds out that the rest five are still looking for the queen in the wrong place and in danger so they set off to save them. As usual, Happy still does the same thing everyday: singing. The episode ends, with the King of the Echoes says "Heigh ho!".