What does infiltrate mean

enter or gain access to (an organization, place, etc.) surreptitiously and gradually, especially in order to acquire information.

the correct answer is:

this is an example of the writer telling through description rather than showing through dialogue.

sometimes writers like to explain explicitely what's happening instead of adding dialogues of the situations., which is the case in this passage,

in night, why are wiesel and his father evacuated from the auschwitz concentration camp? a massive escape makes the nazis question the security of auschwitz. they are assigned to work as laborers in a factory at another camp, buna. hitler has ordered that all remaining jews be relocated within german borders. the german army needs the camp guards to go to the battle front for a last-chance defense.