A strange and fantastic red-and-white striped top hat appears on an empty stage, full of possibilities. A Boy enters and is drawn toward the magical hat. He begins imagining what type of wonderful person would wear such a hat, when The Cat in the Hat suddenly materializes! You ve got quite a mind for your age, quips the Cat as he/she begins singing about the power of imagination ( Oh The Thinks You Can Think ). Throughout the fun and silly song, famous Seussian characters are introduced who will figure in the musical: Horton the Elephant, Gertrude McFuzz the bird with the one feather tail, the Whos of Whoville including the Mayor and his Wife, the General Genghis Kahn Schmitz, Mayzie La Bird, Sour Kangaroo and the Citizens of the Jungle of Nool. As the energizing opening number comes to a close, the Boy and the Cat use their imaginations to transport everyone to the Jungle of Nool for the first adventure ( Horton Hears A Who ). 

Horton is the only one in the jungle with large and sensitive enough ears to hear the tiny citizens of Whoville. They are crying for help as their little planet, the size of a speck of dust, floats aimlessly through air. Horton vows at once to help them and places Whoville safely onto a soft clover, just as Sour Kangaroo and her baby enter the scene. Sour Kangaroo thinks Horton is crazy for talking to and protecting a speck of dust and she lets him and the rest of the jungle know about it ( Biggest Blame Fool ). The rascally Wickersham Brothers a group of mischievous monkeys join in on the fun of teasing Horton. The one person who stands up for Horton, his neighbor Gertrude McFuzz, is not noticed by anyone, most of all Horton. 

Horton is left alone with his inhabited clover and discovers much more about the Whos and their tiny town of Whoville ( Here On Who ). He assures them of his belief that a person s a person no matter how small. The Cat in the Hat, who is continuously present, throws the Boy into the story as JoJo, son to Mr. and Mrs. Mayor of Whoville. They are both very unhappy with JoJo because too many of his thinks have gotten him into trouble at school. They send him to bed, but the Cat in the Hat has another idea ( Oh, The Thinks You Can Think [Reprise]). JoJo s mind begins imagining again and instead of the bathtub, he s swimming in McElligot s pool full of fantastical fish (It s Possible )! The fun is interrupted when Mr. and Mrs. Mayor scold JoJo for flooding the house with bathwater. With JoJo finally in bed, his parents lament the change in him since his thinks began ( How To Raise A Child ). The Cat in the Hat gives them an idea to help solve JoJo s problem and the next morning they introduce their son to 

General Genghis Kahn Schmitz ( The Military ). After a long and very tough first day at military school, JoJo sits alone in his bunk while simultaneously, Horton sits alone guarding the clover ( Alone In The Universe ). Eventually Horton and JoJo hear each other and become friends when they realize their imaginations are so much alike. 

In another part of the jungle, Gertrude has just written her four hundred and thirty-seventh love song about Horton ( The One Feather Tail Of Miss Gertrude McFuzz ). She believes Horton doesn t notice her because of her pathetically small and uninteresting tail. Mayzie appears and offers advice by telling her story ( Amayzing Mayzie ), which leads Gertrude to Doctor Dake and his pills for amayzing feathers. After taking several pills, Gertrude is very happy as her tail begins to grow ( Amayzing Gertrude ), but the Cat in the Hat warns that trouble is brewing. 

The Wickersham Brothers are up to no good ( Monkeying Around ) and they decide to grab the clover with Whoville on it. A chase begins ( Chasing The Whos ) involving Horton, the Wickershams, Sour Kangaroo and the Bad Girls. The Wickershams eventually hand off the clover to Vlad Vladikoff, the eagle, and he taunts and teases, flying and swooping until he drops it. As the clover plummets toward the ground, the Cat in the Hat freezes the action ( How Lucky You Are ), then unfreezes the action and the Whos drop directly onto an enormous field of clover. Though the situation looks bleak, Horton begins looking for the Whos. Gertrude has followed the chase and arrives with her new tail, determined to tell Horton how she truly feels ( Notice Me, Horton ). Horton does not notice and just continues looking for the Whos in the clover. Gertrude leaves rejected and sad. We soon see Mayzie looking bored, sitting up on a nest ( How Lucky You Are [Reprise]) and she convinces Horton to sit on the nest for her while she takes a brief vacation ( Horton Sits On The Egg ). 

Seasons pass and Horton is still stuck sitting on the egg, the Whos are still lost in the clover and Gertrude still cannot get Horton to notice her and her very long tail! ( Horton s Dilemma/The Hunters ). Hunters suddenly arrive to capture Horton and the egg and because of Gertrude s now long and heavy tail, she cannot fly to help Horton. Chaos begins until the Cat freezes the tableau and Horton, Gertrude, the Cat and all the Whos send the audience out to intermission ( How Lucky You Are [Second Reprise]). 

As the orchestra tunes up again, we realize that the conductor is the Cat in the Hat. The music becomes increasingly wild and out of control pages fly, the baton goes crazy, the Cat does his/her tricks until the Cat finally regains control to actually begin Act Two ( Seussical Entr Acte ). 

The Boy runs on to question the Cat about the future of Horton, the egg and JoJo but the Cat just sends the Boy back into the story (as JoJo) without any indication as to what will happen next. 

Horton is still surrounded by hunters as he sits on Mayzie s egg up in the tree. Though the tiny town of Whoville was damaged in the fall , the military school continues to march. JoJo marches, wondering what the point of marching is when their world is in ruins. Back in the jungle, Gertrude is extremely worried about Horton, but can hardly walk without help because her tail is so long and heavy. All the jungle characters watch as Horton, still on the tree nest, is carried away by the hunters ( Egg, Nest and Tree ). After a long, arduous journey, Horton arrives in New York where he is auctioned off to the circus. 

The Cat enters as Mr. McGurkus who proceeds to introduce us to his fantastical circus with Horton as his main attraction ( The Circus McGurkus ). As the circus rambles throughout the country, Horton worries about JoJo and Whoville and wonders when Mayzie will return to her egg; he needs her back now ( The Circus On Tour/How Lucky You Are [Reprise]). The circus arrives in Palm Beach, where we find Mayzie under a palm tree bemoaning the monotony of vacationing ( Mayzie In Palm Beach ). She decides she needs a change of scenery and heads to the circus, where she runs into Horton who begs her to take back her egg. Mayzie sees Horton s adventure with the egg as a great success and decides Horton would be a better parent for her egg than she could ever be ( Amayzing Horton ), so she gives him the egg for good. Horton accepts the responsibility of caring for the egg ( Alone In The Universe [Reprise]), even though he worries about JoJo and the Whos. He sings the egg a lullaby ( Solla Sollew ) that is echoed by JoJo and Mr. and Mrs. Mayor, as JoJo writes, and his parents read, his letter from military school. 

The next morning, General Schmitz and his military cadets head off to war to fight the Butter Side Downers who eat their bread the wrong way ( Green Eggs and Ham II ). JoJo confronts the General about the ridiculousness of the war and quits, marching off in the direction of a minefield. We then hear an extremely loud explosion. 

Back in Whoville, the Christmas pageant is under way led by the Grinch ( Into The Whos Christmas Pageant ) and ends with the traditional finale ( The Grinch Carved The Roast Beast ). General Schmitz suddenly enters with his cadets and approaches Mr. and Mrs. Mayor with horrible news ( A Message From The Front/Solla Sollew [Reprise]). JoJo has been lost in the war a war which has become questionable in everyone s eyes. In re-enacting JoJo s departure, the Cat helps us discover that JoJo has survived, but is confused and lost ( JoJo Alone In The Universe ). Frightened, JoJo begins to blame the Cat for all his troubles, but the Cat helps him find his way home to the arms of his parents ( Havin A Hunch ). 

Far away at the circus, Horton is woken up by Gertrude, who has journeyed great distances and through much peril to find and rescue him. She tells him the reason for her tail mishap and her going through all these adventures is because she cares for him ( All For You ). She also has found the Whos clover! Horton finally notices that Gertrude is amazing. As he begins to communicate with the Whos again, he is interrupted by Sour Kangaroo and the Wickersham Brothers who make a citizens arrest and put Horton on trial for talking to a speck of dust and sitting on an egg. The trial begins ( The People Versus Horton The Elephant ) and everyone becomes more agitated as it progresses especially Horton. When Judge Yertle (the Turtle) sentences Horton to the Nool Asylum and the speck of dust to be boiled in oil, Horton trumpets his protest and tells the Whos they must yell to be heard to prove their existence. They try and they try, but still only Horton can hear them. Suddenly, JoJo comes up with a think: a new word to shout that will be heard by everyone YOPP! At last, all the animals of Nool hear the tiny planet of Whoville and realize Horton was right and the people of Whoville realize what a great thinker JoJo is. Horton and Whoville are saved! Just then, the giant egg begins to crack and out comes an Elephant Bird. Horton looks to Gertrude for help and they agree to care for the creature together ( Yopp!/Alone In The Universe [Reprise]). 

All is well in the Jungle of Nool and in Whoville, but many more adventures are likely to occur if you open your mind, oh, the thinks you will find ( Oh, The Thinks You Can Think [Reprise]). As the song ends, we find the Boy alone onstage with the red and white striped hat which embodies his imagination. As he puts it on, it falls over his eyes putting the stage into BLACKOUT!