Dupaynil thought himself clever. And his assignment, to probe Sassinak's crew for a saboteur was certainly not beyond his ability, but he made a dreadful mistake in thinking that he was smarter than Sassinak.
Dupaynil viewed himself as intelligent. His mission was to uncover the saboteur from Sassinak's crew; it wasn't beyond his abilities, but he failed to recognize that he might not be wiser than Sassinak.