Dracula's Riddle is a game. The goal of the game is to solve riddles and puzzles. You do not need to download any software to play it. Dracula's Riddle is divided in three parts: Dracula's Riddle 1, Dracula's Riddle 2: Part 1 and Dracula's Riddle 2: Part 2. Dracula's Riddle 1 and Dracula's Riddle 2: Part 1 are free to play. To play Dracula's Riddle 2: Part 2, you need to register and donate 5 euros to activate your account (this is a very simple paypal payment and the activiation is automatic and instant). In Dracula's Riddle 2: Part 2, the interface is a bit more advanced.
Dracula's Riddle 1 is an old fashioned linear online riddle game. You solve one riddle, type in the answer in the address bar, and get to the next riddle. This is the game to play if you are of the conservative kind.
Dracula's Riddle 2 is more complex than its prequel. The linearity of Dracula's Riddle 1 is not to be found in this game. Here you will often be presented to multiple choice crossroads where you must choose a path to walk. Each path will have its own trail of riddles. Sometimes, in order for a riddle to be solved, you must use a clue or hint that you have found in some other part of the game, perhaps on a different path.
If you are a first time player, Dracula's Riddle 2: Mist of Deceit is the recommended choice. Its riddles and its entire concept is more thought through and will most likely be more entertaining and also challenging.
Good luck on your quest!