Build a movie plot around this: What happened to Robbie's mind as he took on the simple personality of Pardue? It snapped.
The answer to this question is:
Young Robbie Wheeling (Tom Hanks) plays the Mazes and Monsters game with his friends. They're everything to him; a refuge from his family and the heartbreaks of reality. One day, as he and his friends undertake their first live-action roleplay, Robbie's mind snaps; in that instant, he takes on the simple personality of Pardue, his cleric character in the game. He vanishes, and Lieutenant Martini (Murray Hamilton) suspects foul play, whether accidental or intentional, on the part of his fellow players... until Robbie, in one brief moment of clarity, calls home from distant New York. Returned home, he returns to being Pardue, now safe in the arms of his friends and family, who pray he will someday return to normal.