To achieve the secret ending you need to get all the collectibles (including the last one) after this go to the cornfield chapter and open the hidden door on the ground (in the middle of the cornfield) and after this use this code on the lever to open the door at the right of the room : UP, UP, UP, RIGHT, LEFT, LEFT, LEFT, UP, UP, RIGHT, LEFT, RIGHT, RIGHT, RIGHT
Here's a full summary of the game story :
*SPOILER ALERT* The little boy in the game spend most of the story running away from an evil corporation that transform the poor people into mind controlled slaves for the richer people and in the later chapters the boy infiltrate the building of the evil corporation and long story short end up sucked into a room full of water with a monstrous giant blob monster made of the bodies of many human experiments, the boy (who gained the ability to breath underwater earlier in the game) disconnect the cables attached to the blob monster and get pulled in the monster by one of its many arms. Now that the boy is now *inside* the blob we now control the monster who now has the enormous strenght of all the bodies of the blob ball. The blob breaks free of the water tank and is now loose in the building. The blob cause havok in the entire building destroying many walls and floors, also rolling over many employee and scientists. moments later the blob (literraly) breaks in the office of the CEO of the evil corporation and roll over him causing him to fall to his death and squashed into a pool of blood by the blob. Moments later the employees contain the blob by tricking him into falling into a silo full of water, shortly after, the blob escape from the silo into a storage warehouse and breaks trough a wall that send him rolling in a forest slope and ends up on a beach with the sun shining on the blob, then the credits rolls and The End.
