"Who is going in there?"
Translation:Wie gaat er daarin?
In English, "there" has two different uses. One is to specify a location, and the other is that part of "to be" whose grammatical name I can't remember right now. In Dutch, these are two different words: "daar" and "er" respectively. E.g. the English sentence "There is a dog in there" uses both meanings of "there" - the Dutch translation would be something like "Er staat een hond daarin". In Dutch it's just more obvious which is which.