What did she know that she had to be killed? Was Joe the person keeping tabs on Franks computer when he was watching Katia?
shareI believe the issue was that Brendan was seen with Katia on the night he was murdered. So IA is trying to track her down as a witness to the events of that night.
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I don’t know nuttin 'bout birth'n no baby vampires - Vampy Tara
She was the Eastern European prostitute who lured Antwan Bobek, the man who they found in Brendan's trunk, out of the bar the night he was killed. She could tie Brendan and Joe to that murder, so Joe tried to make her disappear instead of killing her, but that didn't work because Frank kept looking for her.
And yes Joe was the person tracking Frank's computer.
I always say the absence of evidence is not the evidence of absence.
--- Gin Rummy