After Spenser was arrested for assaulting boylan the police chief for thinking he was burying a murder case but the night he got out you were dispatched to a murder which soon turned into Boylans murder and Terrance’s murder and Terrance was framed as a dirty cop which didn’t aline to you as the evidence and motive didn’t line up or make sense. But anyone that was remotely involved or investigating the case was coming as murdered, dirty, or missing but that didn’t stop you from investigating or secretly meeting with Spenser since he was investigating on his time since he wasn’t a cop anymore. But Driscoll and Macklin and probably a good chunk of the cops were dirty are at least that’s what your theory is. Now your sitting in your office trying to link the cases and find out who did it and get the dirty cops off the field and into prison