Lucille: Whoever's behind this whole thing has his connections right in the department. Any leads?
Marv: One guy I talked to told me it was Roark running the show.
Lucille: Whoever it is, he knew I was checking out that hooker almost before I did.
Marv: What hooker?
Lucille: The one you've been obsessing over. The dead one. Goldie.
— Sin City 2005
I don't quite understand these two sentences with the bold words.
Does did refer to "check out" or "know"? What does the sentence mean?
Why is obsessing over being used here? I think it should be you've been obsessed with/by.
According to the dictionary, obsess over means worry about something all the time. I don't think it applies here.
Best Answer
Question 1: What does "did" stand for?
I agree with you that in principle "did" could stand for either "know" or "check out". But let's examine what makes sense in this context:
In my opinion, the first option doesn't make sense because of the tenses: "checked out" implies the action was over, whereas "was checking out" implies the action was in progress.
The second option makes sense when understood as "he knew I was checking her out, even before I realised I was checking her out".
Question 2: "obsessed over" vs "obsessed by/with"
Both are possible in this context. Note, however, that whereas "obsessed over" is a verb, "obsessed by/with" is an adjective. The meaning is essentially the same: