You assume control of Heinrich, an executioner, cursed by the witch Gretchen and rendered immortal. The only way to break the curse is to team up with Gretchen and battle Dr. Faust, who's cursing the land with plague and monsters. It's actually a rather original spin on classic German literature. Unfortunately, none of that creativity seems to carry through in the design.
Gameplay is similar to recent action games a la God of War -- but there's a "twist." The AI-controlled Gretchen follows you into combat, enabling you to access her various witch powers and finishing moves. While you may be immortal, Gretchen is not, so you must balance protecting her and using her as an asset in battle. From what I've observed, immortality doesn't really add to the game. Namco Bandai's own Splatterhouse, for example, takes better advantage of the immortality concept by giving you the ability to swing your limbs at enemies -- even when they're detached from your body!