Milo Murphy's Law Wiki

Some say he doesn't even exist.
But you just said he's the janitor.
Some say I said he's the janitor.

Melissa Chase and Zack Underwood

"The Math Book" is the 20th episode in the first season of Milo Murphy's Law.

Melissa forgot her math book as she retrieves it alongside Milo and Zack. As she retrieves the book from the classroom, however, they forgot to take the key Principal Milder entrusted them with, and as the door of the classroom is locked, they go on a quest to find the janitor, a.k.a. "The Great Key-Keeper".


Milo, Zack, and Melissa return to Jefferson County Middle School after school hours, because Melissa forgot her math book in one of the classrooms. As they head in hoping to find it, Melissa and Milo discuss the existence of the "Great Key-Keeper" aka Fred the janitor, who supposedly sends students on "quests towards enlightenment." After obtaining a key to the classroom from Principal Milder, the trio recover the book, only to forget the key inside the room, which locks behind them. Despite Zack's disbelief, Milo and Melissa then believe that Fred is providing signs that will help them find him so that they can get back into the classroom and recover the key.

The trio's "quest" takes them into the janitorial office, where they encounter Mr. Drako, and then into a locked storeroom that opens up into the old school library. They then discover a secret passage that leads to their science classroom, eventually making their way outside, where Coach Mitchell informs them that he saw someone on the roof. Investigating, they fail to locate Fred but succeed in discovering a roof hatch that enables them to get back into the class to recover the key, which they promptly return to Principal Milder. Fred then appears to Milo and Melissa and asks for their help in cleaning up the mess caused by their "quest." They then try to get Zack's attention so they can show him "The KeyKeeper" but by the time Zack turns around, he's gone.


For a full transcript of "The Math Book", click here.


Click here to view more images from The Math Book.
The image gallery for The Math Book may be viewed here.


Production Information

  • The segment was first released on the Disney XD app prior to its premiere date.


International Airings

  • June 11, 2017 (Hungary)[1]
  • July 7, 2017 (Southeast Asia)
  • August 9, 2017 (Disney Channel Israel)


  • Zack has a secret admirer named Crystal.
  • Milo has a cousin named Reggie.


  • The Pyramids and Stonehenge - There are models of these sites in the janitor's room.
  • "When one door closes, another opens" - When Milo sees a vent to get into a locked room, he quotes a proverb he got from his father, based on this popular saying.


  • When Melissa is trying to take the key from Principal Milder, the desk appears to cut into her waist.
  • When Melissa tells Zack that Crystal is, "The girl who likes you, apparently." A portion of her skirt hem disappears for a second.
  • When Milo, Melissa, and Zack are inside the classroom to get the math book, the stuff on top of the desks changes from one shot to another, and the key disappears in the second shot.
  • Melissa is improperly layered on the background when she reenters the locked classroom.
  • Adrian Pasdar is credited as "Mr. Chase" in this episode, despite the character not appearing in this episode.
  • There were multiple red books on the bookshelf Milo climbed to.

Cast and Characters


'"Battle of the Bands"'
Episodes Next:
'"The Little Engine That Couldn't"'

v - e - d Episodes
Season 1 Going the Extra MiloThe UndergroundersRooting for the EnemySunny Side UpThe Doctor Zone FilesThe NoteParty of PerilSmooth Opera-torWorked DayThe Wilder WestFamily VacationMurphy's LardSecrets and PiesAthledecamathalonThe SubstituteTime OutWe're Going to the ZooSchool DanceBattle of the BandsThe Math BookThe Little Engine That Couldn'tThe Llama IncidentMissing MiloStar StruckDisaster of My DreamsA Clockwork OriginPerchance to SleepwalkSome Like it YachtBackward to School NightWorld Without MiloThe RaceLove TobogganThe Island of Lost DakotasFungus Among UsMilo Murphy's Halloween Scream-A-Torium!A Christmas Peril
Season 2 The Phineas and Ferb EffectSnow Way OutTeacher FeaturePicture DayAgee Ientee DiogeeGame NightPace Makes WasteCake 'Splosion!Lady KrillersDoof's Day OutDisco Do-OverThe Ticking ClockManaging Murphy's LawMilo's ShadowSick DayField of ScreamsSpy Little Sister!Dog Walker, Runner, ScreamerNow I Am a MurphyFreefallMilo's WorldAbducting Murphy's LawThe Goulash LegacyThe Dog Who Knew Too MuchAdventure BuddiesRide Along Little DoggieLook At This ShipCast PartySafety FirstCavendish UnleashedFirst ImpressionsThe Speech and Debate League of Death and Destruction Cross Town Explosion Event‎The Mid-Afternoon Snack ClubParks and WreckEscapeMilo in SpaceSphere and Loathing in Outer Space
v - e - d Secondary Story Arc Episodes
Llama Incident Arc The UndergroundersRooting for the EnemyMurphy's LardWe're Going to the ZooBattle of the BandsThe Llama IncidentMissing Milo
Milo and Amanda Arc Smooth Opera-torSchool DanceCake 'Splosion!Managing Murphy's LawSpy Little Sister!Ride Along Little Doggie
Mr. Drako Arc AthledecamathalonWe're Going to the ZooSchool DanceThe Math BookSome Like it YachtBackward to School NightMilo Murphy's Halloween Scream-A-Torium!Picture Day
Just Getting Started Arc Secrets and PiesSchool DanceBattle of the BandsDisaster of My DreamsManaging Murphy's Law
Lost Dakotas Arc Backward to School NightLove TobogganThe Island of Lost DakotasThe Phineas and Ferb EffectSnow Way Out
Episodes in Italics indicate an episode that doesn't center around the subject of an arc but is still related to it.