Stewart is a whiz-kid. He is super smart at decoding puzzles. He might be too clever by half, because in his search for clues, he makes some up.
His job at ESP is to take suspected encoded psyche-scanned transmissions and uncover the hidden message. It’s a long, slow process, involving many permutations and combinations of words and sounds. But, as they say, ‘if anyone can, he can.’
Stewart is also very young, so he doesn’t understand that what he invents could have deadly implications for others. It’s just a fascinating job to him.
(He would be the one to make sense of Jesus’ death after his resurrection.)