It just popped up on the screen. It's them.

突然从窗口弹出来的是他们
There are only 3 children.

只有三个孩子
There were four when I went to go get you.

我去找你的时候还有四个
What is this on their faces?

他们脸上盖着什么
They look like gas masks.

像是防毒面具
Why would you fill a place with gas and then provide gas masks?

既然布置成了毒气室为何又配上防毒面具
Well, maybe the gas serves another purpose.

毒气可能是另作他用
Such as?

有什么用
Well, look how evenly they're spaced out.

看他们的位置分布均匀
And the hoses are stretched

管子的长度限制了活动范围
as far as they can go without coming off.

他们只能在这个长度以内走动
The masks are to keep them in specific positions.

面具将每个人的位置固定了下来