Molly tries to say "It's time for Bubble Guppies!" but she sees Gil organizing books. When he suddenly says "Fish" he is startled! But this allows the little fish to say "It's time for Bubble Guppies" instead.
Molly is on her way to school when she sees Bubble Puppy and Gil sitting outside of the library. She sees Gil reading and he just finishes before mentioning that he had to bring back his library books today, but he wanted to read them a final time. He shows Molly his library card and sadly deposits his books. When he tries to open the door but it doesn't. he realizes it's closed, so he instead puts them into the book slot nearby. After he says goodbye to his most favorite book, Molly mentions that she wishes the library was open so that she could get some books too. With that in mind the two little guppies swim to class.
At school Gil explains that he borrowed some books from the library and he had to stop and take them back. Nonny explains what Borrowing means as Mr. Grouper and Gil show their library cards. Gil begins to worry upon realizing his card is missing!
Mr. Grouper tells Gil if the card doesn't turn up then he can always get a new one. Although the look on Gil's face shows that he doesn't want a new card, he likes his old one. This causes Deema to ask what a Librarian is. So Mr. Grouper begins to explain what one can do at a library. Like read newspapers, magazines, and books. If you want to borrow a book then you need a Library Card. All books can be found on shelves.Moly then sings: Check It Out!.
Deema decides she will be a Librarian for her very own Library! Goby comes by to check out a book and he asks her for a book about penguins. Deema looks it up using her computer, then she gets Goby a book. But he doesn't think its a penguin book, it's one about cows! Deema then asks the viewers for help to find the penguin book. She asks what a penguin is, person, place, or animal. Then she looks on the Animal shelf for the Penguin book.
She then asks if a penguin is a bird, dinosaur, or fish. Then looks on the middle shelf to find the penguin book! She then checks out the book using Goby's library book.
Nonny makes the lunch joke: Chiken sandwich and liberry juice.
Gil asks Molly what she's reading about and she shows him her princess book. The little fish as Gil to read to them and so he begins to read about the Ocean... Suddenly a whole bunch of water shoots out on him!
In class the guppies are making their own books using crayons and paper. Molly and Oona agree to make a book together, Oona decides she'll be the illustrator and Molly asks what Deema will be writing about. Deema wants to write about herself while Gil is too sad about losing his Library card to even make one. Deema then shows her book she's made.
The guppies go outside to play, Oona and Deema are pretending to be sailors. Goby tells the story of two brave sailors who travel to the Island of the Cyclups. Nonny pops in to explain what a Cyclops is, which makes Deema begin to worry. Oona explains that inside the cave is every book to read, in the WHOLE world. So they go inside and come to the very giant library inside the cave. Oona shows Deema the book about ducklings when they suddenly hear noise approaching and find a spot to hide from the cyclops.
Oona and Deema try to flee when Deema is distracted by a book about monkies! They find a section about baby animals and go inside to take a look. They find baby bunnies, hippo's, and many others. So they look at every single book until the cyclops returns. Oona and Deema hurriedly put away the books in order to avoid detection but Oona realizes that they messed up and put the wrong books on the people shelf. Then they go to a wild animal shelf, then hide again. Oona sees that they accidentally forgot to put away the kitten book, the book the cyclops is looking for...
Deema holds out her hand, but the cyclops manages to find them hiding behind the cart anyway. So the girls quickly flee, only for the cyclops to be outside waiting for them! Deema runs and hides behind a stone while he tells Oona they can borrow the books anytime they want, as long as they bring them back. And so, the cyclops and sailors became friends and they all lived happily ever after... Then Gil sings: Turn The Page.
Molly mentions that so many things can be found in the pages of books before she greets Gil. He shows her the story of camels he found when the little fish come back. They ask him to read to them again and when he does, water sprays him again!
Mr. Grouper comes by to tell them that the Library is open now and all the Guppies head on over to ask the Librarian if she's found his library card.
The librarian greets Gil as Gil explains what happened. She tells him that she hasn't seen his card, then offers to get him a brand new one. Gil sees that she has the books he brought back and he begins to theorize that maybe the card was left between one of the pages. This makes Gil begin to imagine himself as a secret agent inside the book while searching for his card...
He meets with Agent 3, who hasn't seen his library card. Gil continues to search, not finding it inside that book. So he checks his Knight book. Gil talks to the Knight, who has not seen his library card again. The dragon too tells him that he hasn't seen it. So the final book to check is the humungous book of dinosaurs. Gil then has to decide which shelf to check, the humans, dinosaur, or buildings. He looks inside the middle shelf and into the book. A big dinosaur sneaks up on Gil and he quickly flees from the big dinosaur for many pages until cornered!
The dinosaur then asks if he is Gil, then shows him the Library Card! Gil has successfully found his library card! Everyone congradulates him and he asks to check out the dinosaur book again, now calling it his most favorite, favorite book. The Librarian then asks the guppies if they want a library card too as the episode ends...
Molly shows Gil the Princess book she checked out while he shows her a circus book he picked. He says he is happy there isn't any water... only for an elephant trunk to pop out and spray him!