Angel Code: A Linda Hyde Mystery is a hidden-object adventure game with a touch of supernatural. The protagonist of the story is Linda Hyde, a New York reporter who one day receives an email from an Italian law firm telling her she inherited a mansion. Not sure if it was a joke or not as she doesn't know nor have any relatives in Italy, she calls the law firm to inquire about the contents of this email. It turns out to be real and she really did inherit a mansion there, and her traveling expenses are covered as well just in case she may hesitate to believe. Upon her arrival she notices the mansion in question is the same mansion she recently dreamed about. Upon further investigation, she uncovers an old Templar ring which sets her on the journey to find The Whole Grail. But her adventure soon turns dangerous as it turns out she is not the only one trying to find the cup of Christ. The adventure takes her through various European locales and countries such as Italy, France, and Scotland, and on her quest she teams up with Raphael, a guide she met in France who is none other than her guardian angel, figuratively and literally.
The game doesn't feature a typical load/save progress system, instead it saves on key locations and you can just continue the story from the account (which is just the player's name) that you've played it. While the game provides some basic gameplay hints whenever you encounter something new, there are no texts or mouse cursor highlights when you hover over key object you can click on. The mana-like potion on the lower left part of the screen fills in slowly which when pressed highlights the next point of interest on your current location, whether you are just investigating around or searching for hidden objects. When solving puzzles, that potion turns to auto-solve button which solves and skips the current puzzle.
During hidden-object search, the objects you have to find to progress the story randomly changes except the key objects that you have to find in order to put them in your inventory. While in investigation mode, you can use objects from your inventory against objects on the screen (e.g. use axe on lock to break it). Story is split into several chapters which are told in different locations of your quest, and voice acting is full supported for all characters during the conversation and key thoughts, while occasional conversations during investigation does not feature voice-acting, but only text. Various mini-games and puzzles entail trying to find the proper object that fits at a given place, jigsaw puzzle where you try to mend torn book pages or other fragmented objects, or unlocking doors. At dangerous situations there is a stealth mode where you have to sneak past the guard or enemy combatant by slowly moving from one location to another without getting spotted.