Belief is a powerful thing; we often fail to realize how important it is to focus on the positive in ourselves to overcome adverse external factors.  The first panel of page 28, Volume II of Maus is a wide view, focusing a lot on the surroundings of the mice, including the chimney out the window that inspires such terror.  Overwhelmed by his seemingly dire situation, Vladek begins to cry in the second panel; all he metaphorically sees (and all we literally see through the window above him) is darkness.  In the third, a priest arrives, notably blocking out the window through which the terrifying chimneys might otherwise have been seen; his concern temporarily distracts Vladek from his misery.  In the fourth, however, when Vladek responds angrily, trying to refocus on the cause of his misery (likely not to risk the psychological pain of gaining hope only to lose it), the darkness is once again visible through the window.  The priest persists, however, and in the fifth panel, the darkness is again shut out as Vladek begins to have hope again.  The priest inspects Vladek's number and provides him with several reasons the numbers mean Vladek will survive.  The priest could, I'm sure, have come up with positive ways to interpret the six digits on Vladek's arm no matter what each digit actually was, because this priest is determined to view things in a positive way.  The belief he spreads to Vladek allows Vladek to focus not on his surroundings, but on himself, which is paralleled by the fact that Vladek's arm enlarges in each of the three panels in which the priest proclaims the numbers' significance.  As Vladek focuses on what he views as positive, and doesn't allow his surroundings to defeat him, the window stays out of view: focusing in on something hopeful allows Vladek to escape the "panes" the window represents.