I don't quite get the structure of this sentence. How can "something" be a subject of the sentence?

Native speaker’s answer
Rebecca
Good question! "Something" can be a subject of a sentence since it's a pronoun! The same way another noun or pronoun can be a subject of a sentence. "Something" indicates a thing that is unspecified or unknown. The sentence itself is past-perfect continuous, "had+ past participle [done]," meaning that an action was completed before a point of time in the past! So "something" completed "something else." Ex: When I got home, I saw something on the table. Ex: Something was on the table. Ex: Something had happened to her last night, but I wasn't sure what.