Mystery Man

"It appears they didn't understand its true purpose."

- The Man referring to Daniel Curien's vital.

"Goldman, you are soft. These wretched humans have no need for hope. Soon the true end shall begin. There is more than one Pandora's box!"

- The Man. "So Pandora's Box has been closed. That is if there is any "hope" left. The Wheel of Fate cannot be stopped."

- The Man in the lab.

Thornheart, also known as The Mystery Man by fans, is a mysterious man and one of the main antagonists who appeared in the House of the Dead series. He is a business suit who walks with a noticeable limp. He first appeared in one of the endings for The House of the Dead III, and appeared again in one of the endings for The House of the Dead 4, Special. He is the main antagonist of The House of the Dead: Scarlet Dawn.

History
Not much is known his true identity. Since nothing else was known at the time, many have speculated his true identity at the ending of HOTD2.

The Mystery Man was shown to harbor a strong contempt for humanity, believing they are beyond hope, unlike his colleague Goldman. It has yet to be revealed what his motives and goals are, as well as his previous ties to both Curien and Goldman.

The House of the Dead II
Right before Goldman commit suicide, he mention that a "successor" will come, it is possible that the "successor" is Thornheart.

The House of the Dead III
He is seen walking in the chamber where the Wheel of Fate was defeated and picks up a glowing canister revealed earlier as Daniel's cure. As he holds it in his hands, he chuckles to himself saying, "It appears that he didn't understand its true purpose," and then walks off.

The House of the Dead 4
He walks in to a office and sits down at the desk, and saying "Goldman, you are soft. These wretched humans have no need of hope. Soon, the true end shall begin. ...There is more than one Pandora's Box."

The House of the Dead 4: Special
In the "Good Ending" of the game, The Mystery Man appears where the protagonists Kate Green and G fought The Magician, and saying "So, Pandora's Box has been closed. That is, if there is any "hope" left. The Wheel of Fate cannot be stopped."

The House of the Dead: Scarlet Dawn
In the trailer, he is seen at a dinner party, unleashing zombies on to the dinner guests and saying "Run until you all die!".

Trivia

 * He appears different and slightly older in The House of the Dead 4 ending compared to what he looked like from The House of the Dead III ending. This is strange, as The House of the Dead III takes place several years after The House of the Dead 4. Although it could be because he could barely be seen in the House of the Dead III ending, or that the developers of the game decided to slightly retcon his appearance.
 * If you noticed in The House Of The Dead 4 ending, you can almost see that on the mystery man does not have a foot on the damaged leg.
 * He had a resemblance to the character the G-Man from the Half-Life series. He even had a middle aged gaunt appearance, plus a widow peak hairstyle like the G-Man, and is seen dressed in a suit. The G-Man is also a mysterious entity in the Half-Life series, with his real identity not disclosed.
 * His laugh in his ending in The House of the Dead III somewhat resembles Goldman's laugh from The House of the Dead 2.