In the previous chapter, I alluded to the fact that there were many types of Masks false fronts that can cover up an NPC's deep fear, shame, emotional wound, or problem.
Sometimes, however, a person puts up a false front for just a minute or two a temporary false front. Consider an example: The hypothetical game is staged in a modern-day war located in a third-world country. You fight your way to the base, encountering one enemy after another. When you arrive, the Base Commander is there, waiting.
He seems cheerful that reinforcements are coming, and says thank God the worst is over.
You go to check in with whomever is going to give you your next mission. But on the way out, using Eavesdrop Mode, you overhear the Base Commander telling another officer how worried he is about the situation. Even with reinforcements, he thinks the group is doomed.
The emotion being covered up doesn't always have to be negative. For instance, an NPC could cover up love with feigned indifference.
The reason he hasn't told you or the other soldiers is that he didn't want to lessen morale. He presented you with a false emotion, covering a darker one. This gives him depth.