Father O'Malley has defeated the Zombie Lord, and forestalled the apocalypse. But now he must escape from the Crypts of Na'uta before they are consumed in a fiery sea of destruction. Drained from his battle with the Zombie Lord, Father O'Malley must struggle to the surface with his last ounces of strength.
(This is a truly absurd game that got less development time than it deserved -- but I think it's probably still good for a chuckle and a few minutes of fun. It was also a first experiment with the Flixel engine: http://flixel.org/)
By the way, for anyone who might be wondering: you didn't miss parts 1 and 2 -- in keeping with the entire idea being ridiculous and silly, part 3 is the first game in the O'Malley series.
Use the left and right arrow keys to move, and the up arrow to jump.
Press X to throw a cross (crosses will destroy zombies, naturally).
Touching a zombie will kill Father O'Malley; letting the rising lava touch him will have a similar effect.
Run to the right edge of each level as quickly as possible to avoid the lava and advance to the next level. There are 20 levels in total, with the number of zombies and the rate at which the lava rises increasing in each level.
(Protip: during the second or two when the zombies are climbing out of the ground, they cannot kill you, so it is possible to run through them at the very instant they appear, with a little luck.)
You can control the volume the the + and - keys, and mute with the zero key.
(If the game appears to be ignoring your keystrokes, you might just need to give it an initial click.)