to keep Harry safe. Later he returns it to Harry after resigning his post at Hogwarts. From then on, the map becomes one of Harry's most useful tools in his ongoing adventures. When not in use, the Map is simply a blank piece of parchment. It can be activated by pointing a wand at it and saying, "I solemnly swear that I am up to no good", at which point the message "Messrs. Moony, Wormtail, Padfoot and Prongs, purveyors of aids to magical mischief-makers, are proud to present the Marauder's Map" appears, along with a detailed layout of Hogwarts. The map is restored to its original blank state by saying "Mischief managed". The map displays the location of everyone within the castle and its grounds. It includes locations of secret passageways and instructions on how to access them. Several locations like the Room of Requirement and the Chamber of Secrets do not appear on the map, either as the Marauders did not have any knowledge of them, or, in the case of the former, they are not a fixed location. Animagus disguises, Polyjuice Potion, and invisibility cloaks cannot fool the map. In Prisoner of Azkaban, Peter Pettigrew, who is supposed to be dead but as an Animagus has transformed into a rat, shows up on the map under his real name. In Goblet of Fire, Barty Crouch Jr. is using Polyjuice Potion to disguise himself as Moody. At one point, Harry catches him on the map searching Snape's office for ingredients, but mistakes him for his father, Barty Crouch Sr., as the map cannot differentiate between two individuals who share a first and last name. Crouch Jr. subsequently confiscates the map from Harry, and uses it to track down and murder his own father when his father breaks free of the Imperius Curse and comes to Hogwarts looking for him. On the prop version of the map made for the films, the lines are made up of what at first glance are just random letters, but upon closer inspection are Latin words. The series makes no mention of Harry recovering the map from Crouch Jr.'s office, even though he continued to use it in later books; when asked about this discrepancy, J. K. Rowling answered that Harry had indeed sneaked into the office and recovered it in the days following the Third Task, and that she had forgotten to include