Well,
So know we know that the original conflict of interest with Elliot working for both clients was a pretty significant clue. I'm wondering if the money in the cigarette case was for Elliott to prevent him from saying anything to Jeff. Also, it's not improbable that the money was flowing from Elliott to Annette. Maybe they made a deal to share the extra cash that Jeff was paying Elliott until Annette left. I'm wondering if she was going to announce that she was the mole on Monday and also quit at the same time. This gives Elliott a pretty strong motive to kill her so that the truth didn't come out about him. Everyone would have been pretty suspicious that he hadn't found out about her... I'm also wondering if these "late night" working sessions may have been more than just pretending to work on a case that they both knew was pointless.
Meg's slip about the "accident" is also interesting, though it may be nothing. She still doesn't have an alibi, though. Could she have gone into the office and seen whomever killed Annette? Or found the body first and covered up for someone?
Sophia lawyered up pretty fast in her 3rd interview, but I don't really see a reason for her to kill Annette.
All of this still doesn't discount Darren as the possible killer. I still like him for this, but we haven't heard anything from Kurt or Johanna about the stealthy car mystery. Does anyone have any other ideas?