Klaus Baudelaire is the middle Baudelaire child and has read more books than most people do in a lifetime. He is always there to help Violet and Sunny with words they don't understand and has a photographic memory.
Klaus is known to be very book smart, and remembers and processes just about everything he reads. He has read almost every book in the Bauldelaire library, and has read everything he can in the V.F.D. library in the Mortmain Mountains hideout and everything he has time to read anywhere else. This makes him an excellent researcher, and his researching skills often help the Baudelaire children to foil Count Olaf's evil schemes.
He wears glasses, and can barely see without them.
Klaus lived with his parents and sisters Violet and Sunny until he was twelve years old, at which time his house was burned to the ground by Count Olaf while he, Sunny, and Violet were hanging out at Briny Beach. The Baudelaire parents were killed in the fire, making Klaus, Sunny, and Violet orphans. He and his sisters were sent to live with the evil Count Olaf, who forced them to do all of his chores and treated them abysmally. He tried to gain control of the fantastic Baudelaire fortune by tricking Violet into marrying him during a play, but due to Klaus's researching skills his plot was foiled, and Olaf was almost arrested, although he escaped due to the incompetence of Mr. Poe, the banker in charge of finding good guardians for the Baudelaire orphans.
Klaus, Violet, and Sunny were transferred to Uncle Monty, their new guardian. They live a kind of peaceful life, and they are ready to go to Peru when Stephano (Count Olaf) becomes Uncle Monty's assistant. Stephano murders Uncle Monty with poison but thanks to Violet's invention of a lockpick and Klaus's research about the Mambu du Mal they make Mr. Poe realize that he is Count Olaf.
Klaus and his sisters were transferred to Aunt Josephine. His only toy there was a rattle. Captain Sham (Count Olaf) appears and threatens Josephine to write a note that will leave the children to his care. Josephine faked her death. Klaus then decode a message from Aunt Josephine's suicidal note. It read Curdled Cave. They went there and convinced Josephine to come back. Josephine didn't want to so Klaus said that the cave was for sale and there will be realtors. Klaus sees Aunt Josephine get thrown to the leeches and calls Olaf a fiend.
Klaus, Violet, and Sunny worked at Lucky Smells Lumbermill and were paid in coupons, which was later revealed to be illegal. Klaus was hypnotized after breaking his glasses twice by the evil Dr. Orwell and had Violet and Sunny worried about him.
Klaus, Sunny, and Violet met Duncan and Isadora Quagmire when they were sent to a boarding school; Prufrock Preparatory School. A friendship developed between Klaus and Isadora, from whom Klaus learned the usefulness of a case book.
Violet, Sunny, and Klaus meet up again with the Quagmire triplets who are caged in Esme's house. Klaus read a catalog and states (wrongly) that the Quagmires are inside the VFD (very fancy doilies). But they are really hidden in Lot #49, a red haering with them unseen.
He reads about mob psychology and the rules of the village which unfortunately was too late because Jacques Snicket is already murdered mysteriously by Olaf. He spends his 13th birthday in jail in this book and eats bread and drinks water.
Klaus types a telegram to Arthur Poe about what happened to them. He and Sunny also almost killed Violet by pretending as the 2 white faced women. He stalled to keep Violet alive. They find the last page of the Snicket file which is safely kept in his pocket.
Klaus, along with Violet, pretend to be a two headed freak along with in the Caligari Carnival. His name in disguise is Elliot. At the end, Count Olaf traps Klaus and Violet in a moving caravan and takes Sunny away with him and his troupe. 
Klaus helps Violet to stop the rolling caravan and search for poor Sunny. They also meet up with Quigley Quagmire who Violet has some romantic interest in. Klaus starts his own commonplace book that Quigley gave him. He helped decode using the Verbal Fridge Dialogue that the VFD meeting will be on Thursday. They managed to rescue Sunny from Count Olaf's clutches after she signals them with Esme's green cigarette. They learn of the sugar bowl, which is revealed to be stolen by Lemony Snicket, and not Beatrice their mother.
Violet, Klaus and Sunny are under the sea in this book. They meet Captain Widdershins and Fiona, who Klaus shares a special relationship with. Captain Windershinns is quite the man you need to get use to. Captain Widdershins shows them a big black question mark, called the Great Unknown. Then he sends the children and Fiona out into the sea to the grotto (cave) where the sugar bowl is. The sugar bowl ends up not to be there. Fiona tells Violet, Klaus, and Sunny about the Medusoid Mycelium and how dangerous and poisonous it is. She recites the poem: "A single spore has such grim power, that you may die within the hour. Is dilution simple? But of course! Just one small dose of root of horse." Soon after that, Sunny ends up getting sick and starts dying from the Medusoid Mycelium. Klaus, Fiona, and Violet try to find a way to save her. Luckily they find wasabi that had horseradish and give it to Sunny. She gets better. Fiona later joins Count Olaf and his troupe (which has the hook-handed man, who's her brother Fernald, in it). Klaus has his first kiss with Fiona before saying good-bye. They go to Briny Beach and meet Kit Snicket in a taxi. 
Klaus and his sisters pretend to be concierges.Kit tells them that Ernest in on the other side of V.F.D. and Frank is on their side but they are twins. Klaus realized that the sugar bowl was delivered by a crow. He opens the Vernacularly Fastened Door using three codes (possibly VFD) and comes with Olaf in escaping the Hotel Denouement.
Violet, Klaus and Sunny wash up with Count Olaf on a deserted island filled with people. They were then deserted on the coastal shelf with Olaf and Kit Snicket, who was very pregnant at the time. At the end, Kit and Count Olaf die of the Medusoid Mycelim as Kit is giving birth to her baby, little Beatrice. Klaus, Violet, Sunny, and Beatrice proceeded to leave. It's a mystery on whether or not they survived, as their boat, the Beatrice, sank when they were near the mainland. <r It wass said that Klaus would spend a lot of time thinking about his present situation many years later, so it is implied that he had survived.
- The Dismal Dinner
- The Bad Beginning (First appearance)
- The Reptile Room
- The Wide Window
- The Miserable Mill
- The Austere Academy
- The Ersatz Elevator
- The Vile Village
- The Hostile Hospital
- The Carnivorous Carnival
- The Slippery Slope
- The Grim Grotto
- The Penultimate Peril
- The End
Notes and referencessEdit
- ↑ The Bad Beginning
- ↑ The Reptile Room
- ↑ The Wide Window
- ↑ The Miserable Mill
- ↑ The Austere Academy
- ↑ The Ersatz Elevator
- ↑ The Vile Village
- ↑ The Hostile Hospital
- ↑ The Carnivorous Carnival
- ↑ The Slippery Slope
- ↑ The Grim Grotto
- ↑ The Penultimate Peril
- ↑ The End
- ↑ Chapter Fourteen
- ↑ The Reptile Room