In truth one would almost always say "it's nighttime," not just night.
I also never heard It is night, maybe it is the night or it's (the) nighttime
It's quite poetic. Dramatic. Under Milk Wood by Dylan Thomas.
Maybe it's just regional or bad American english, but I think its totally normal to say it's night
In English, you can also say they are in hiding, and they went into hiding, but perhaps that's a bit too idiomatic: more for someone wanted for arrest or to be interviewed or beaten up than simply hiding. Gangster owls?