The Professor's Trunk is an item that Professor Layton takes with him on his adventures.
This item allows Luke and Layton to view their progress and investigation. There are 7 different items inside (8 in Professor Layton and the Diabolical Box). The first one is Layton's Journal. Here, Layton keeps all of his thoughts on the investigation at hand. The next item is the Mysteries section. Here, Layton and Luke can see where they stand in the game and what strange things they have witnessed. The next item is the Puzzle Index. Layton and Luke can access all of the puzzles they have solved previously. This section is also in the Bonus area as well. After that is a spot to Save the game. Once clicked, Layton and Luke can save the game by then tapping on the correct save file. Below these four items are three silhouetted figures. These figures are the minigames that Layton and Luke obtain on their adventures.
In Professor Layton and the Curious Village, Layton tells Luke about this suitcase he has with him. Luke is told how to use this item while Layton and Luke are investigating the plaza in St. Mystere. Layton explains what the trunk does and what it is used for. Layton finds various Painting Scraps and Mechanical Parts on his adventure throughout St. Mystere. Also, to glorify their rooms at the local Inn, Layton and Luke find many items such as beds, tables, books, and chairs for their rooms at the Inn.
Here, Layton and Luke discuss the trunk in the Professor's Study at the very beginning of the game. Later on, Luke and Layton confront the chef of the Molentary Express, Macaroon. Macaroon has a pet hamster that isn't very fit as it has eaten many delicious foods aboard the Molentary Express. This hamster becomes the first minigame. Aboard the train, Layton finds Sammy Thunder, the conductor. Sammy accidentally broke the camera his Uncle, Mr. Beluga, owns. Layton offers to help fix the device and heads off. At Dropstone, Layton and Luke find a kind elderly lady named Laurel. Laurel, out of the kindness of her heart, gives Layton and Luke a Tea Set as their final Minigame. At Folsense, Layton and Luke discover a strange Old Diary. This Diary is later revealed to belong to Anton Herzen, the current Duke of Folsense. This Diary then is added into the trunk even though there is no spot for it.
In the third game, Layton and Luke use this trunk in the same fashion and they discuss using it on the way through Midland Road. At Anita's, a cafe in Midland Road of Future London, a man named Alfie walks up to Luke and gives him the picture book. Luke uses this item as the first minigame. There is another minigame that Luke and Layton obtain at the Hotel Duke. This item in particular is the Toy Car. This car also is given to Luke. Much later in the game, Luke, with the help of Future Luke, takes a Parrot down from Graham near by. Luke receives the Parrot upon helping Graham. This Parrot is the minigame, but it isn't until after Chapter 4, when Luke can perform it. Stachenscarfen gives Layton and Luke the idea to help out those in need of deliveries with this Parrot. This allows Luke to access the final minigame.
Last Specter adds a few new items into the regular mix of the trunk. Aside from the three regular minigames, three new additions were made (Four for the US release). At the bottom of the trunk are three options: a memo option to jot down various pieces of information if the need arises; the new Collection area which offers 24 different collectible items throughout Misthallery, each of which has two descriptions, one for Layton and Luke respectively; for the US release of Last Specter, which includes Professor Layton's London Life, a small button can be pressed to open up London Life. Doing so ends the current Last Specter game without saving. The last new feature in Layton's trunk is the Episodes, which add more the side plot of the game. More episodes are unlocked by beating certain parts of the storyline, and beating side-missions.