、。
She closed the door and went upstairs.
Literal
She [topic-は] door [object-を] closed [then-て], second-floor [to-に] went-up.
Two sequential actions chained with the te-form: 閉めて ('having closed') leads into 上がった ('went up'). 上がる ('go up') is the standard verb for ascending — stairs, elevation, rank — and pairs naturally with 階 ('floor, level'). Note that traditional Japanese homes were typically single-story, with 二階 reserved for grand or modern dwellings; in modern apartments and houses 二階建て (two-story) is common but still distinct enough to mention by name. The sentence has the rhythm of a short story line: action, then action.